{"id":50755,"date":"2023-12-23T10:31:41","date_gmt":"2023-12-23T02:31:41","guid":{"rendered":"https:\/\/www.silicloud.com\/zh\/blog\/java%e7%bc%96%e7%a8%8b%e9%9d%a2%e8%af%95%e9%97%ae%e9%a2%98%e7%9a%84%e5%89%8d50%e5%90%8d\/"},"modified":"2023-12-23T15:03:10","modified_gmt":"2023-12-23T07:03:10","slug":"java%e7%bc%96%e7%a8%8b%e9%9d%a2%e8%af%95%e9%97%ae%e9%a2%98%e7%9a%84%e5%89%8d50%e5%90%8d","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/zh\/blog\/java%e7%bc%96%e7%a8%8b%e9%9d%a2%e8%af%95%e9%97%ae%e9%a2%98%e7%9a%84%e5%89%8d50%e5%90%8d\/","title":{"rendered":"Java\u7f16\u7a0b\u9762\u8bd5\u95ee\u9898\u7684\u524d50\u540d"},"content":{"rendered":"

\u4ecb\u7ecd<\/h3>\n

\u5982\u679c\u4f60\u6b63\u5728\u9762\u8bd5Java\u7f16\u7a0b\u89d2\u8272\uff0c\u90a3\u4e48\u4f60\u7684\u7f16\u7801\u80fd\u529b\u53ef\u80fd\u4f1a\u53d7\u5230\u8003\u9a8c\u3002\u65e0\u8bba\u4f60\u662fJava\u521d\u5b66\u8005\u8fd8\u662f\u4e13\u5bb6\u7a0b\u5e8f\u5458\uff0c\u672c\u6587\u63d0\u4f9b\u4e86\u4e00\u4e9b\u5e38\u89c1\u7684Java\u9762\u8bd5\u95ee\u9898\u548c\u7b54\u6848\uff0c\u4ee5\u5e2e\u52a9\u4f60\u505a\u597d\u51c6\u5907\u3002<\/p>\n

\u5728Java\u4e2d\u5982\u4f55\u53cd\u8f6c\u5b57\u7b26\u4e32?<\/h2>\n

\u5728String\u7c7b\u4e2d\u6ca1\u6709reverse()\u5de5\u5177\u65b9\u6cd5\u3002\u7136\u800c\uff0c\u60a8\u53ef\u4ee5\u4ece\u5b57\u7b26\u4e32\u521b\u5efa\u4e00\u4e2a\u5b57\u7b26\u6570\u7ec4\uff0c\u7136\u540e\u4ece\u672b\u5c3e\u5230\u5f00\u5934\u8fed\u4ee3\u5b83\u3002\u60a8\u53ef\u4ee5\u5c06\u5b57\u7b26\u6dfb\u52a0\u5230\u4e00\u4e2a\u5b57\u7b26\u4e32\u6784\u5efa\u5668\u4e2d\uff0c\u6700\u540e\u8fd4\u56de\u53cd\u8f6c\u540e\u7684\u5b57\u7b26\u4e32\u3002<\/p>\n

\u4ee5\u4e0b\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u4e00\u79cd\u53cd\u8f6c\u5b57\u7b26\u4e32\u7684\u65b9\u6cd5\uff1a<\/p>\n

public<\/span> class<\/span> StringPrograms<\/span> {<\/span>\r\n\r\n\tpublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>\r\n\t\tString<\/span> str =<\/span> \"123\"<\/span>;<\/span>\r\n\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>reverse<\/span>(<\/span>str)<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n\tpublic<\/span> static<\/span> String<\/span> reverse<\/span>(<\/span>String<\/span> in)<\/span> {<\/span>\r\n\t\tif<\/span> (<\/span>in ==<\/span> null<\/span>)<\/span>\r\n\t\t\tthrow<\/span> new<\/span> IllegalArgumentException<\/span>(<\/span>\"Null is not valid input\"<\/span>)<\/span>;<\/span>\r\n\r\n\t\tStringBuilder<\/span> out =<\/span> new<\/span> StringBuilder<\/span>(<\/span>)<\/span>;<\/span>\r\n\r\n\t\tchar<\/span>[<\/span>]<\/span> chars =<\/span> in.<\/span>toCharArray<\/span>(<\/span>)<\/span>;<\/span>\r\n\r\n\t\tfor<\/span> (<\/span>int<\/span> i =<\/span> chars.<\/span>length -<\/span> 1<\/span>;<\/span> i >=<\/span> 0<\/span>;<\/span> i--<\/span>)<\/span>\r\n\t\t\tout.<\/span>append<\/span>(<\/span>chars[<\/span>i]<\/span>)<\/span>;<\/span>\r\n\r\n\t\treturn<\/span> out.<\/span>toString<\/span>(<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
\u5728\u65b9\u6cd5\u4e2d\u6dfb\u52a0\u7a7a\u503c\u68c0\u67e5\u5e76\u4f7f\u7528StringBuilder\u6765\u8ffd\u52a0\u5b57\u7b26\uff0c\u5c06\u4f1a\u83b7\u5f97\u5956\u52b1\u5206\u3002\u8bf7\u6ce8\u610f\uff0c\u5728Java\u4e2d\u7d22\u5f15\u4ece0\u5f00\u59cb\uff0c\u6240\u4ee5\u5728for\u5faa\u73af\u4e2d\u5e94\u4ecechars.length – 1 \u5f00\u59cb\u3002<\/p>\n
\u5728Java\u4e2d\uff0c\u4e0d\u4f7f\u7528\u7b2c\u4e09\u4e2a\u53d8\u91cf\uff0c\u4f60\u5982\u4f55\u4ea4\u6362\u4e24\u4e2a\u6570\u5b57\uff1f<\/h2>\n
\u4e0d\u4f7f\u7528\u7b2c\u4e09\u4e2a\u53d8\u91cf\u8fdb\u884c\u4ea4\u6362\u6570\u5b57\u662f\u4e00\u4e2a\u4e09\u6b65\u9aa4\u7684\u8fc7\u7a0b\uff0c\u5728\u4ee3\u7801\u4e2d\u66f4\u5bb9\u6613\u8fdb\u884c\u53ef\u89c6\u5316\u3002<\/p>\n
b = b + a; \/\/ now b is sum of both the numbers\r\na = b - a; \/\/ b - a = (b + a) - a = b (a is swapped)\r\nb = b - a; \/\/ (b + a) - b = a (b is swapped)\r\n<\/code><\/pre>\n
\u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u4e00\u79cd\u5b9e\u73b0\u6570\u5b57\u4ea4\u6362\u65b9\u6cd5\u7684\u65b9\u5f0f\uff1a<\/p>\n
public<\/span> class<\/span> SwapNumbers<\/span> {<\/span>\r\n\r\npublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>\r\n\tint<\/span> a =<\/span> 10<\/span>;<\/span>\r\n\tint<\/span> b =<\/span> 20<\/span>;<\/span>\r\n\r\n    System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"a is \"<\/span> +<\/span> a +<\/span> \" and b is \"<\/span> +<\/span> b)<\/span>;<\/span>\r\n\r\n\ta =<\/span> a +<\/span> b;<\/span>\r\n\tb =<\/span> a -<\/span> b;<\/span>\r\n\ta =<\/span> a -<\/span> b;<\/span>\r\n\r\n    System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"After swapping, a is \"<\/span> +<\/span> a +<\/span> \" and b is \"<\/span> +<\/span> b)<\/span>;<\/span>\r\n    }<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
\u8f93\u51fa\u663e\u793a\u6574\u6570\u503c\u5df2\u4ea4\u6362\u3002<\/p>\n
\r\nOutput\r\n\r\na is 10 and b is 20 After swapping, a is 20 and b is 10\r\n<\/code><\/pre>\n
\u5199\u4e00\u4e2aJava\u7a0b\u5e8f\u6765\u68c0\u67e5\u4e00\u4e2a\u5b57\u7b26\u4e32\u4e2d\u662f\u5426\u5b58\u5728\u5143\u97f3\u5b57\u6bcd\u3002<\/h2>\n
\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528\u6b63\u5219\u8868\u8fbe\u5f0f\u6765\u68c0\u67e5\u5b57\u7b26\u4e32\u662f\u5426\u5305\u542b\u5143\u97f3\u5b57\u6bcd\u3002<\/p>\n
public<\/span> class<\/span> StringContainsVowels<\/span> {<\/span>\r\n\r\n\tpublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>stringContainsVowels<\/span>(<\/span>\"Hello\"<\/span>)<\/span>)<\/span>;<\/span> \/\/ true<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>stringContainsVowels<\/span>(<\/span>\"TV\"<\/span>)<\/span>)<\/span>;<\/span> \/\/ false<\/span>\r\n\t}<\/span>\r\n\r\n\tpublic<\/span> static<\/span> boolean<\/span> stringContainsVowels<\/span>(<\/span>String<\/span> input)<\/span> {<\/span>\r\n\t\treturn<\/span> input.<\/span>toLowerCase<\/span>(<\/span>)<\/span>.<\/span>matches<\/span>(<\/span>\".*[aeiou].*\"<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
\u5199\u4e00\u4e2aJava\u7a0b\u5e8f\u6765\u68c0\u67e5\u7ed9\u5b9a\u7684\u6570\u5b57\u662f\u5426\u662f\u8d28\u6570\u3002<\/h2>\n
\u4f60\u53ef\u4ee5\u7f16\u5199\u4e00\u4e2a\u7a0b\u5e8f\uff0c\u5c06\u7ed9\u5b9a\u7684\u6570\u5b57n\u9664\u4ee52\u5230n\/2\u4e4b\u95f4\u7684\u6570\u5b57\uff0c\u5e76\u68c0\u67e5\u4f59\u6570\u3002\u5982\u679c\u4f59\u6570\u4e3a0\uff0c\u5219\u5b83\u4e0d\u662f\u4e00\u4e2a\u8d28\u6570\u3002\u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u4e00\u79cd\u68c0\u67e5\u7ed9\u5b9a\u6570\u5b57\u662f\u5426\u4e3a\u8d28\u6570\u7684\u65b9\u6cd5\uff1a<\/p>\n
public<\/span> class<\/span> PrimeNumberCheck<\/span> {<\/span>\r\n\r\n\tpublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>isPrime<\/span>(<\/span>19<\/span>)<\/span>)<\/span>;<\/span> \/\/ true<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>isPrime<\/span>(<\/span>49<\/span>)<\/span>)<\/span>;<\/span> \/\/ false<\/span>\r\n\t}<\/span>\r\n\r\n\tpublic<\/span> static<\/span> boolean<\/span> isPrime<\/span>(<\/span>int<\/span> n)<\/span> {<\/span>\r\n\t\tif<\/span> (<\/span>n ==<\/span> 0<\/span> ||<\/span> n ==<\/span> 1<\/span>)<\/span> {<\/span>\r\n\t\t\treturn<\/span> false<\/span>;<\/span>\r\n\t\t}<\/span>\r\n\t\tif<\/span> (<\/span>n ==<\/span> 2<\/span>)<\/span> {<\/span>\r\n\t\t\treturn<\/span> true<\/span>;<\/span>\r\n\t\t}<\/span>\r\n\t\tfor<\/span> (<\/span>int<\/span> i =<\/span> 2<\/span>;<\/span> i <=<\/span> n \/<\/span> 2<\/span>;<\/span> i++<\/span>)<\/span> {<\/span>\r\n\t\t\tif<\/span> (<\/span>n %<\/span> i ==<\/span> 0<\/span>)<\/span> {<\/span>\r\n\t\t\t\treturn<\/span> false<\/span>;<\/span>\r\n\t\t\t}<\/span>\r\n\t\t}<\/span>\r\n\r\n\t\treturn<\/span> true<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
\u5c3d\u7ba1\u8fd9\u4e2a\u7a0b\u5e8f\u80fd\u591f\u6b63\u5e38\u5de5\u4f5c\uff0c\u4f46\u5b83\u5728\u5185\u5b58\u548c\u65f6\u95f4\u6548\u7387\u4e0a\u8868\u73b0\u4e0d\u4f73\u3002\u8bf7\u8003\u8651\u4ee5\u4e0b\u60c5\u51b5\uff1a\u5bf9\u4e8e\u7ed9\u5b9a\u6570N\uff0c\u5982\u679c\u57282\u5230\u221aN\uff08N\u7684\u5e73\u65b9\u6839\uff09\u4e4b\u95f4\u5b58\u5728\u4e00\u4e2a\u80fd\u591f\u6574\u9664N\u7684\u8d28\u6570M\uff0c\u90a3\u4e48N\u5c31\u4e0d\u662f\u4e00\u4e2a\u8d28\u6570\u3002<\/p>\n
\u5199\u4e00\u4e2a\u4f7f\u7528\u9012\u5f52\u7684Java\u7a0b\u5e8f\uff0c\u6253\u5370\u51fa\u4e00\u4e2a\u6590\u6ce2\u90a3\u5951\u5e8f\u5217\u3002<\/h2>\n
\u6590\u6ce2\u90a3\u5951\u6570\u5217\u662f\u4e00\u79cd\u6bcf\u4e2a\u6570\u5b57\u90fd\u662f\u524d\u4e24\u4e2a\u6570\u5b57\u4e4b\u548c\u7684\u6570\u5217\u3002\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c\u6570\u5217\u4ece0\u548c1\u5f00\u59cb\u3002\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528for\u5faa\u73af\u6253\u5370\u6590\u6ce2\u90a3\u5951\u6570\u5217\u3002<\/p>\n
public<\/span> class<\/span> PrintFibonacci<\/span> {<\/span>\r\n\r\n\tpublic<\/span> static<\/span> void<\/span> printFibonacciSequence<\/span>(<\/span>int<\/span> count)<\/span> {<\/span>\r\n\t\tint<\/span> a =<\/span> 0<\/span>;<\/span>\r\n\t\tint<\/span> b =<\/span> 1<\/span>;<\/span>\r\n\t\tint<\/span> c =<\/span> 1<\/span>;<\/span>\r\n\r\n\t\tfor<\/span> (<\/span>int<\/span> i =<\/span> 1<\/span>;<\/span> i <=<\/span> count;<\/span> i++<\/span>)<\/span> {<\/span>\r\n\t\t\tSystem<\/span>.<\/span>out.<\/span>print<\/span>(<\/span>a +<\/span> \", \"<\/span>)<\/span>;<\/span>\r\n\r\n            a =<\/span> b;<\/span>\r\n\t\t\tb =<\/span> c;<\/span>\r\n\t\t\tc =<\/span> a +<\/span> b;<\/span>\r\n\t\t}<\/span>\r\n\t}<\/span>\r\n\r\n\tpublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>\r\n    \tprintFibonacciSequence<\/span>(<\/span>10<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
\r\nOutput\r\n\r\n0, 1, 1, 2, 3, 5, 8, 13, 21, 34,\r\n<\/code><\/pre>\n
\u4f60\u4e5f\u53ef\u4ee5\u4f7f\u7528\u9012\u5f52\u6765\u6253\u5370\u6590\u6ce2\u90a3\u5951\u6570\u5217\uff0c\u56e0\u4e3a\u6590\u6ce2\u90a3\u5951\u6570\u662f\u901a\u8fc7\u5728\u5e8f\u5217\u4e2d\u52a0\u4e0a\u524d\u4e24\u4e2a\u6570\u5b57\u751f\u6210\u7684\u3002<\/p>\n
F(N) = F(N-1) + F(N-2)\r\n<\/code><\/pre>\n
\u4e0b\u9762\u7684\u793a\u4f8b\u7c7b\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528\u9012\u5f52\u6765\u8ba1\u7b97\u957f\u5ea6\u4e3a10\u7684\u6590\u6ce2\u90a3\u5951\u6570\u5217\u3002<\/p>\n
public<\/span> class<\/span> PrintFibonacciRecursive<\/span> {<\/span>\r\n\r\n    public<\/span> static<\/span> int<\/span> fibonacci<\/span>(<\/span>int<\/span> count)<\/span> {<\/span>\r\n\t\tif<\/span> (<\/span>count <=<\/span> 1<\/span>)<\/span>\r\n\t\t\treturn<\/span> count;<\/span>\r\n\r\n\t\treturn<\/span> fibonacci<\/span>(<\/span>count -<\/span> 1<\/span>)<\/span> +<\/span> fibonacci<\/span>(<\/span>count -<\/span> 2<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n\tpublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span> args[<\/span>]<\/span>)<\/span> {<\/span>\r\n    \tint<\/span> seqLength =<\/span> 10<\/span>;<\/span>\r\n\r\n    \tSystem<\/span>.<\/span>out.<\/span>print<\/span>(<\/span>\"A Fibonacci sequence of \"<\/span> +<\/span> seqLength +<\/span> \" numbers: \"<\/span>)<\/span>;<\/span>\r\n\r\n    \tfor<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> seqLength;<\/span> i++<\/span>)<\/span> {<\/span>\r\n      \t    System<\/span>.<\/span>out.<\/span>print<\/span>(<\/span>fibonacci<\/span>(<\/span>i)<\/span> +<\/span> \" \"<\/span>)<\/span>;<\/span>\r\n    \t}<\/span>\r\n  \t}<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
\r\nOutput\r\n\r\nA Fibonacci sequence of 10 numbers: 0 1 1 2 3 5 8 13 21 34\r\n<\/code><\/pre>\n
\u5728Java\u4e2d\uff0c\u4f60\u5982\u4f55\u68c0\u67e5\u4e00\u4e2a\u6574\u6570\u5217\u8868\u662f\u5426\u53ea\u5305\u542b\u5947\u6570\uff1f<\/h2>\n
\u4f60\u53ef\u4ee5\u4f7f\u7528\u4e00\u4e2afor\u5faa\u73af\uff0c\u5e76\u68c0\u67e5\u6bcf\u4e2a\u5143\u7d20\u662f\u5426\u4e3a\u5947\u6570\u3002<\/p>\n
public<\/span> static<\/span> boolean<\/span> onlyOddNumbers<\/span>(<\/span>List<\/span><<\/span>Integer<\/span>><\/span><\/span> list)<\/span> {<\/span>\r\n\tfor<\/span> (<\/span>int<\/span> i :<\/span> list)<\/span> {<\/span>\r\n\t\tif<\/span> (<\/span>i %<\/span> 2<\/span> ==<\/span> 0<\/span>)<\/span>\r\n\t\t\treturn<\/span> false<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n\treturn<\/span> true<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
\u5982\u679c\u5217\u8868\u5f88\u5927\uff0c\u60a8\u53ef\u4ee5\u4f7f\u7528\u5e76\u884c\u6d41\u8fdb\u884c\u66f4\u5feb\u7684\u5904\u7406\uff0c\u5982\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u6240\u793a\uff1a<\/p>\n
public<\/span> static<\/span> boolean<\/span> onlyOddNumbers<\/span>(<\/span>List<\/span><<\/span>Integer<\/span>><\/span><\/span> list)<\/span> {<\/span>\r\n\treturn<\/span> list\r\n\t\t\t.<\/span>parallelStream<\/span>(<\/span>)<\/span> \/\/ parallel stream for faster processing<\/span>\r\n\t\t\t.<\/span>anyMatch<\/span>(<\/span>x -><\/span> x %<\/span> 2<\/span> !=<\/span> 0<\/span>)<\/span>;<\/span> \/\/ return as soon as any elements match the condition<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
\u82e5\u8981\u4e86\u89e3\u5224\u65ad\u6574\u6570\u662f\u5426\u4e3a\u5947\u6570\u7684\u6570\u5b66\u80cc\u540e\uff0c\u8bf7\u53c2\u8003\u7ef4\u57fa\u767e\u79d1\u4e0a\u7684\u6a21\u8fd0\u7b97\u3002<\/p>\n
7. \u5728Java\u4e2d\uff0c\u4f60\u5982\u4f55\u68c0\u67e5\u4e00\u4e2a\u5b57\u7b26\u4e32\u662f\u5426\u662f\u56de\u6587\uff1f<\/h2>\n
\u56de\u6587\u4e32\u662f\u6307\u6b63\u5e8f\u548c\u5012\u5e8f\u90fd\u76f8\u540c\u7684\u5b57\u7b26\u4e32\u3002\u8981\u68c0\u67e5\u4e00\u4e2a\u5b57\u7b26\u4e32\u662f\u5426\u4e3a\u56de\u6587\u4e32\uff0c\u53ef\u4ee5\u5c06\u8f93\u5165\u5b57\u7b26\u4e32\u53cd\u8f6c\u5e76\u68c0\u67e5\u7ed3\u679c\u662f\u5426\u4e0e\u8f93\u5165\u76f8\u7b49\u3002\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528String charAt(int index)\u65b9\u6cd5\u6765\u68c0\u67e5\u56de\u6587\u4e32\uff1a<\/p>\n
boolean<\/span> checkPalindromeString<\/span>(<\/span>String<\/span> input)<\/span> {<\/span>\r\n\tboolean<\/span> result =<\/span> true<\/span>;<\/span>\r\n\tint<\/span> length =<\/span> input.<\/span>length<\/span>(<\/span>)<\/span>;<\/span>\r\n\r\n\tfor<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> length\/<\/span>2<\/span>;<\/span> i++<\/span>)<\/span> {<\/span>\r\n\t\tif<\/span> (<\/span>input.<\/span>charAt<\/span>(<\/span>i)<\/span> !=<\/span> input.<\/span>charAt<\/span>(<\/span>length -<\/span> i -<\/span> 1<\/span>)<\/span>)<\/span> {<\/span>\r\n\t\t\tresult =<\/span> false<\/span>;<\/span>\r\n\t\t\tbreak<\/span>;<\/span>\r\n\t\t}<\/span>\r\n\t}<\/span>\r\n\r\n\treturn<\/span> result;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
8. \u5728Java\u4e2d\uff0c\u5982\u4f55\u53bb\u9664\u5b57\u7b26\u4e32\u4e2d\u7684\u7a7a\u683c\uff1f<\/h2>\n
\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u4f7f\u7528Character.isWhitespace()\u65b9\u6cd5\u4ece\u5b57\u7b26\u4e32\u4e2d\u5220\u9664\u7a7a\u683c\u7684\u4e00\u79cd\u65b9\u6cd5\u3002<\/p>\n
String<\/span> removeWhiteSpaces<\/span>(<\/span>String<\/span> input)<\/span> {<\/span>\r\n\tStringBuilder<\/span> output =<\/span> new<\/span> StringBuilder<\/span>(<\/span>)<\/span>;<\/span>\r\n\t\r\n\tchar<\/span>[<\/span>]<\/span> charArray =<\/span> input.<\/span>toCharArray<\/span>(<\/span>)<\/span>;<\/span>\r\n\t\r\n\tfor<\/span> (<\/span>char<\/span> c :<\/span> charArray)<\/span> {<\/span>\r\n\t\tif<\/span> (<\/span>!<\/span>Character<\/span>.<\/span>isWhitespace<\/span>(<\/span>c)<\/span>)<\/span>\r\n\t\t\toutput.<\/span>append<\/span>(<\/span>c)<\/span>;<\/span>\r\n\t}<\/span>\r\n\t\r\n\treturn<\/span> output.<\/span>toString<\/span>(<\/span>)<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
\u4e86\u89e3\u5982\u4f55\u5728Java\u4e2d\u5220\u9664\u5b57\u7b26\u4e32\u4e2d\u7684\u7a7a\u683c\u548c\u5176\u4ed6\u5b57\u7b26\u3002<\/p>\n
9. \u5728Java\u4e2d\uff0c\u4f60\u5982\u4f55\u53bb\u9664\u5b57\u7b26\u4e32\u7684\u524d\u5bfc\u548c\u5c3e\u968f\u7a7a\u683c\uff1f<\/h2>\n
String\u7c7b\u5305\u542b\u4e24\u4e2a\u65b9\u6cd5\u6765\u5220\u9664\u524d\u5bfc\u548c\u5c3e\u968f\u7684\u7a7a\u683c\uff1atrim()\u548cstrip()\u3002strip()\u65b9\u6cd5\u662f\u5728Java 11\u4e2d\u6dfb\u52a0\u5230String\u7c7b\u4e2d\u7684\u3002strip()\u65b9\u6cd5\u4f7f\u7528Character.isWhitespace()\u65b9\u6cd5\u6765\u68c0\u67e5\u5b57\u7b26\u662f\u5426\u4e3a\u7a7a\u683c\u3002\u8fd9\u4e2a\u65b9\u6cd5\u4f7f\u7528Unicode\u4ee3\u7801\u70b9\uff0c\u800ctrim()\u65b9\u6cd5\u5c06\u4efb\u4f55\u4ee3\u7801\u70b9\u503c\u5c0f\u4e8e\u6216\u7b49\u4e8eU+0020\u7684\u5b57\u7b26\u6807\u8bc6\u4e3a\u7a7a\u683c\u5b57\u7b26\u3002<\/p>\n
strip()\u65b9\u6cd5\u662f\u63a8\u8350\u7684\u53bb\u9664\u7a7a\u767d\u5b57\u7b26\u7684\u65b9\u5f0f\uff0c\u56e0\u4e3a\u5b83\u4f7f\u7528\u4e86Unicode\u6807\u51c6\u3002\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528strip()\u65b9\u6cd5\u53bb\u9664\u7a7a\u767d\u5b57\u7b26\u3002<\/p>\n
String<\/span> s =<\/span> \"  abc  def\\t\"<\/span>;<\/span>\r\n\t\t\r\ns =<\/span> s.<\/span>strip<\/span>(<\/span>)<\/span>;<\/span>\r\n\t\t\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s)<\/span>;<\/span>\r\n<\/code><\/pre>\n
\u7531\u4e8e\u5b57\u7b26\u4e32\u662f\u4e0d\u53ef\u53d8\u7684\uff0c\u6240\u4ee5\u60a8\u5fc5\u987b\u5c06strip()\u7684\u8f93\u51fa\u8d4b\u7ed9\u8be5\u5b57\u7b26\u4e32\u3002<\/p>\n
10. \u5728Java\u4e2d\u5982\u4f55\u5bf9\u6570\u7ec4\u8fdb\u884c\u6392\u5e8f\uff1f<\/h2>\n
Arrays\u5de5\u5177\u7c7b\u6709\u8bb8\u591a\u91cd\u8f7d\u7684sort()\u65b9\u6cd5\uff0c\u53ef\u4ee5\u7528\u4e8e\u6392\u5e8f\u539f\u59cb\u6570\u7ec4\u548c\u5bf9\u8c61\u6570\u7ec4\u3002\u5982\u679c\u8981\u6309\u7167\u81ea\u7136\u987a\u5e8f\u5bf9\u539f\u59cb\u6570\u7ec4\u8fdb\u884c\u6392\u5e8f\uff0c\u53ef\u4ee5\u4f7f\u7528Arrays.sort()\u65b9\u6cd5\uff0c\u5982\u4e0b\u4f8b\u6240\u793a:<\/p>\n
int<\/span>[<\/span>]<\/span> array =<\/span> {<\/span>1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>,<\/span> -<\/span>1<\/span>,<\/span> -<\/span>2<\/span>,<\/span> 4<\/span>}<\/span>;<\/span>\r\n\r\nArrays<\/span>.<\/span>sort<\/span>(<\/span>array)<\/span>;<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>Arrays<\/span>.<\/span>toString<\/span>(<\/span>array)<\/span>)<\/span>;<\/span>\r\n<\/code><\/pre>\n
\u7136\u800c\uff0c\u5982\u679c\u4f60\u60f3\u8981\u5bf9\u4e00\u4e2a\u5bf9\u8c61\u6570\u7ec4\u8fdb\u884c\u6392\u5e8f\uff0c\u90a3\u4e48\u8fd9\u4e2a\u5bf9\u8c61\u5fc5\u987b\u5b9e\u73b0Comparable\u63a5\u53e3\u3002\u5982\u679c\u4f60\u60f3\u8981\u6307\u5b9a\u6392\u5e8f\u7684\u6807\u51c6\uff0c\u4f60\u53ef\u4ee5\u4f20\u5165Comparator\u6765\u5b9a\u4e49\u6392\u5e8f\u903b\u8f91\u3002\u5728Java\u4e2d\u4e86\u89e3\u66f4\u591a\u5173\u4e8eComparable\u548cComparator\u7684\u77e5\u8bc6\u3002<\/p>\n
11. \u5982\u4f55\u5728Java\u4e2d\u4ee5\u7f16\u7a0b\u65b9\u5f0f\u521b\u5efa\u6b7b\u9501\u573a\u666f\uff1f<\/h2>\n
\u6b7b\u9501\u662f\u5728\u591a\u7ebf\u7a0bJava\u73af\u5883\u4e2d\u7684\u4e00\u79cd\u60c5\u51b5\uff0c\u5176\u4e2d\u4e24\u4e2a\u6216\u66f4\u591a\u7ebf\u7a0b\u88ab\u6c38\u4e45\u963b\u585e\u3002\u6b7b\u9501\u7684\u60c5\u51b5\u53d1\u751f\u5728\u81f3\u5c11\u4e24\u4e2a\u7ebf\u7a0b\u4e4b\u95f4\u3002\u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u521b\u5efa\u4e86\u4e00\u4e2a\u6b7b\u9501\u60c5\u666f\u3002<\/p>\n
public<\/span> class<\/span> ThreadDeadlock<\/span> {<\/span>\r\n\r\n    public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> throws<\/span> InterruptedException<\/span> {<\/span>\r\n        Object<\/span> obj1 =<\/span> new<\/span> Object<\/span>(<\/span>)<\/span>;<\/span>\r\n        Object<\/span> obj2 =<\/span> new<\/span> Object<\/span>(<\/span>)<\/span>;<\/span>\r\n        Object<\/span> obj3 =<\/span> new<\/span> Object<\/span>(<\/span>)<\/span>;<\/span>\r\n    \r\n        Thread<\/span> t1 =<\/span> new<\/span> Thread<\/span>(<\/span>new<\/span> SyncThread<\/span>(<\/span>obj1,<\/span> obj2)<\/span>,<\/span> \"t1\"<\/span>)<\/span>;<\/span>\r\n        Thread<\/span> t2 =<\/span> new<\/span> Thread<\/span>(<\/span>new<\/span> SyncThread<\/span>(<\/span>obj2,<\/span> obj3)<\/span>,<\/span> \"t2\"<\/span>)<\/span>;<\/span>\r\n        Thread<\/span> t3 =<\/span> new<\/span> Thread<\/span>(<\/span>new<\/span> SyncThread<\/span>(<\/span>obj3,<\/span> obj1)<\/span>,<\/span> \"t3\"<\/span>)<\/span>;<\/span>\r\n        \r\n        t1.<\/span>start<\/span>(<\/span>)<\/span>;<\/span>\r\n        Thread<\/span>.<\/span>sleep<\/span>(<\/span>5000<\/span>)<\/span>;<\/span>\r\n        t2.<\/span>start<\/span>(<\/span>)<\/span>;<\/span>\r\n        Thread<\/span>.<\/span>sleep<\/span>(<\/span>5000<\/span>)<\/span>;<\/span>\r\n        t3.<\/span>start<\/span>(<\/span>)<\/span>;<\/span>        \r\n    }<\/span>\r\n\r\n}<\/span>\r\n\r\nclass<\/span> SyncThread<\/span> implements<\/span> Runnable<\/span> {<\/span>\r\n\r\n    private<\/span> Object<\/span> obj1;<\/span>\r\n    private<\/span> Object<\/span> obj2;<\/span>\r\n\r\n    public<\/span> SyncThread<\/span>(<\/span>Object<\/span> o1,<\/span> Object<\/span> o2)<\/span> {<\/span>\r\n        this<\/span>.<\/span>obj1 =<\/span> o1;<\/span>\r\n        this<\/span>.<\/span>obj2 =<\/span> o2;<\/span>\r\n    }<\/span>\r\n\r\n    @Override<\/span>\r\n    public<\/span> void<\/span> run<\/span>(<\/span>)<\/span> {<\/span>\r\n        String<\/span> name =<\/span> Thread<\/span>.<\/span>currentThread<\/span>(<\/span>)<\/span>.<\/span>getName<\/span>(<\/span>)<\/span>;<\/span>\r\n\r\n        System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>name +<\/span> \" acquiring lock on \"<\/span> +<\/span> obj1)<\/span>;<\/span>\r\n        synchronized<\/span> (<\/span>obj1)<\/span> {<\/span>\r\n            System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>name +<\/span> \" acquired lock on \"<\/span> +<\/span> obj1)<\/span>;<\/span>\r\n            work<\/span>(<\/span>)<\/span>;<\/span>\r\n            System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>name +<\/span> \" acquiring lock on \"<\/span> +<\/span> obj2)<\/span>;<\/span>\r\n            synchronized<\/span> (<\/span>obj2)<\/span> {<\/span>\r\n                System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>name +<\/span> \" acquired lock on \"<\/span> +<\/span> obj2)<\/span>;<\/span>\r\n                work<\/span>(<\/span>)<\/span>;<\/span>\r\n            }<\/span>\r\n            System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>name +<\/span> \" released lock on \"<\/span> +<\/span> obj2)<\/span>;<\/span>\r\n        }<\/span>\r\n        System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>name +<\/span> \" released lock on \"<\/span> +<\/span> obj1)<\/span>;<\/span>\r\n        System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>name +<\/span> \" finished execution.\"<\/span>)<\/span>;<\/span>\r\n    }<\/span>\r\n\r\n    private<\/span> void<\/span> work<\/span>(<\/span>)<\/span> {<\/span>\r\n        try<\/span> {<\/span>\r\n            Thread<\/span>.<\/span>sleep<\/span>(<\/span>30000<\/span>)<\/span>;<\/span>\r\n        }<\/span> catch<\/span> (<\/span>InterruptedException<\/span> e)<\/span> {<\/span>\r\n            e.<\/span>printStackTrace<\/span>(<\/span>)<\/span>;<\/span>\r\n        }<\/span>\r\n    }<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
\u6240\u6709\u4e09\u4e2a\u7ebf\u7a0b\u90fd\u80fd\u591f\u9501\u5b9a\u7b2c\u4e00\u4e2a\u5bf9\u8c61\u3002\u4f46\u662f\uff0c\u5b83\u4eec\u6b63\u5728\u4f7f\u7528\u5171\u4eab\u8d44\u6e90\uff0c\u5e76\u4e14\u4ee5\u4e00\u79cd\u65e0\u9650\u7b49\u5f85\u6765\u542f\u52a8\uff0c\u4ee5\u83b7\u53d6\u7b2c\u4e8c\u4e2a\u5bf9\u8c61\u7684\u9501\u5b9a\u3002\u60a8\u53ef\u4ee5\u4f7f\u7528Java\u7ebf\u7a0b\u8f6c\u50a8\u6765\u68c0\u6d4b\u6b7b\u9501\u3002\u4e86\u89e3\u66f4\u591a\u6709\u5173Java\u4e2d\u6b7b\u9501\u7684\u4fe1\u606f\u3002<\/p>\n
\u5982\u4f55\u5728Java\u4e2d\u627e\u5230\u6574\u6570\u7684\u9636\u4e58\uff1f<\/h2>\n
\u4e00\u4e2a\u6574\u6570\u7684\u9636\u4e58\u662f\u901a\u8fc7\u5c06\u4ece1\u5230\u7ed9\u5b9a\u6570\u5b57\u7684\u6240\u6709\u6570\u5b57\u76f8\u4e58\u6765\u8ba1\u7b97\u7684\u3002<\/p>\n
F(n) = F(1)*F(2)...F(n-1)*F(n)\r\n<\/code><\/pre>\n
\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528\u9012\u5f52\u6765\u8ba1\u7b97\u4e00\u4e2a\u6574\u6570\u7684\u9636\u4e58\u3002<\/p>\n
public<\/span> static<\/span> long<\/span> factorial<\/span>(<\/span>long<\/span> n)<\/span> {<\/span>\r\n\tif<\/span> (<\/span>n ==<\/span> 1<\/span>)<\/span>\r\n\t\treturn<\/span> 1<\/span>;<\/span>\r\n\telse<\/span>\r\n\t\treturn<\/span> (<\/span>n *<\/span> factorial<\/span>(<\/span>n -<\/span> 1<\/span>)<\/span>)<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
13. \u5982\u4f55\u5728Java\u4e2d\u53cd\u8f6c\u4e00\u4e2a\u94fe\u8868\uff1f<\/h2>\n
LinkedList\u7684descendingIterator()\u65b9\u6cd5\u8fd4\u56de\u4e00\u4e2a\u4ee5\u76f8\u53cd\u987a\u5e8f\u904d\u5386\u5143\u7d20\u7684\u8fed\u4ee3\u5668\u3002\u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528\u6b64\u8fed\u4ee3\u5668\u4ee5\u76f8\u53cd\u987a\u5e8f\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u94fe\u8868\uff0c\u5176\u4e2d\u5143\u7d20\u6309\u76f8\u53cd\u987a\u5e8f\u5217\u51fa\u3002<\/p>\n
LinkedList<\/span><<\/span>Integer<\/span>><\/span><\/span> ll =<\/span> new<\/span> LinkedList<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>\r\n\r\nll.<\/span>add<\/span>(<\/span>1<\/span>)<\/span>;<\/span>\r\nll.<\/span>add<\/span>(<\/span>2<\/span>)<\/span>;<\/span>\r\nll.<\/span>add<\/span>(<\/span>3<\/span>)<\/span>;<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>ll)<\/span>;<\/span>\r\n\r\nLinkedList<\/span><<\/span>Integer<\/span>><\/span><\/span> ll1 =<\/span> new<\/span> LinkedList<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>\r\n\r\nll.<\/span>descendingIterator<\/span>(<\/span>)<\/span>.<\/span>forEachRemaining<\/span>(<\/span>ll1::<\/span>add<\/span>)<\/span>;<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>ll1)<\/span>;<\/span>\r\n<\/code><\/pre>\n
\u4ece\u6570\u636e\u7ed3\u6784\u548c\u7b97\u6cd5\u7684\u89d2\u5ea6\u66f4\u591a\u5730\u4e86\u89e3\u5982\u4f55\u9006\u8f6c\u94fe\u8868\u3002<\/p>\n
14. \u5728Java\u4e2d\u5982\u4f55\u5b9e\u73b0\u4e8c\u5206\u67e5\u627e\uff1f<\/h2>\n
\u4e3a\u4e86\u5b9e\u73b0\u4e8c\u5206\u67e5\u627e\uff0c\u6570\u7ec4\u5143\u7d20\u5fc5\u987b\u88ab\u6392\u5e8f\u3002\u4e8c\u5206\u67e5\u627e\u7b97\u6cd5\u57fa\u4e8e\u4ee5\u4e0b\u6761\u4ef6\uff1a<\/p>\n
    \n
  • If the key is less than the middle element, then you now need to search only in the first half of the array.<\/li>\n
  • If the key is greater than the middle element, then you need to search only in the second half of the array.<\/li>\n
  • If the key is equal to the middle element in the array, then the search ends.<\/li>\n
  • Finally, if the key is not found in the whole array, then it should return -1. This indicates that the element is not present.<\/li>\n<\/ul>\n
    \u4ee5\u4e0b\u662f\u4e00\u4e2a\u5b9e\u73b0\u4e8c\u5206\u67e5\u627e\u7684\u793a\u4f8b\u4ee3\u7801\u3002<\/p>\n
    public<\/span> static<\/span> int<\/span> binarySearch<\/span>(<\/span>int<\/span> arr[<\/span>]<\/span>,<\/span> int<\/span> low,<\/span> int<\/span> high,<\/span> int<\/span> key)<\/span> {<\/span>\r\n\tint<\/span> mid =<\/span> (<\/span>low +<\/span> high)<\/span> \/<\/span> 2<\/span>;<\/span>\r\n\r\n\twhile<\/span> (<\/span>low <=<\/span> high)<\/span> {<\/span>\r\n\t\tif<\/span> (<\/span>arr[<\/span>mid]<\/span> <<\/span> key)<\/span> {<\/span>\r\n\t\t\tlow =<\/span> mid +<\/span> 1<\/span>;<\/span>\r\n\t\t}<\/span> else<\/span> if<\/span> (<\/span>arr[<\/span>mid]<\/span> ==<\/span> key)<\/span> {<\/span>\r\n\t\t\treturn<\/span> mid;<\/span>\r\n\t\t}<\/span> else<\/span> {<\/span>\r\n\t\t\thigh =<\/span> mid -<\/span> 1<\/span>;<\/span>\r\n\t\t}<\/span>\r\n\t\tmid =<\/span> (<\/span>low +<\/span> high)<\/span> \/<\/span> 2<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n\tif<\/span> (<\/span>low ><\/span> high)<\/span> {<\/span>\r\n\t\treturn<\/span> -<\/span>1<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n\treturn<\/span> -<\/span>1<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u8bf7\u7f16\u5199\u4e00\u4e2aJava\u7a0b\u5e8f\u6765\u6f14\u793a\u5f52\u5e76\u6392\u5e8f\u3002<\/h2>\n
    \u5f52\u5e76\u6392\u5e8f\u662f\u5176\u4e2d\u4e00\u4e2a\u6548\u7387\u6700\u9ad8\u7684\u6392\u5e8f\u7b97\u6cd5\u4e4b\u4e00\u3002\u5b83\u57fa\u4e8e\u201c\u5206\u800c\u6cbb\u4e4b\u201d\u7684\u539f\u5219\u8fdb\u884c\u64cd\u4f5c\u3002\u5b83\u7684\u601d\u60f3\u662f\u5c06\u5217\u8868\u9010\u6e10\u5206\u89e3\u4e3a\u591a\u4e2a\u5b50\u5217\u8868\uff0c\u76f4\u5230\u6bcf\u4e2a\u5b50\u5217\u8868\u53ea\u5305\u542b\u4e00\u4e2a\u5143\u7d20\uff0c\u7136\u540e\u4ee5\u4e00\u79cd\u4f7f\u7ed3\u679c\u4e3a\u6392\u5e8f\u5217\u8868\u7684\u65b9\u5f0f\u5408\u5e76\u8fd9\u4e9b\u5b50\u5217\u8868\u3002\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u4f7f\u7528\u5f52\u5e76\u6392\u5e8f\u7684\u4e00\u79cd\u65b9\u5f0f\u3002<\/p>\n
    public<\/span> class<\/span> MergeSort<\/span> {<\/span>\r\n\r\n\tpublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>\r\n\t\tint<\/span>[<\/span>]<\/span> arr =<\/span> {<\/span> 70<\/span>,<\/span> 50<\/span>,<\/span> 30<\/span>,<\/span> 10<\/span>,<\/span> 20<\/span>,<\/span> 40<\/span>,<\/span> 60<\/span> }<\/span>;<\/span>\r\n\r\n\t\tint<\/span>[<\/span>]<\/span> merged =<\/span> mergeSort<\/span>(<\/span>arr,<\/span> 0<\/span>,<\/span> arr.<\/span>length -<\/span> 1<\/span>)<\/span>;<\/span>\r\n\r\n\t\tfor<\/span> (<\/span>int<\/span> val :<\/span> merged)<\/span> {<\/span>\r\n\t\t\tSystem<\/span>.<\/span>out.<\/span>print<\/span>(<\/span>val +<\/span> \" \"<\/span>)<\/span>;<\/span>\r\n\t\t}<\/span>\r\n\t}<\/span>\r\n\r\n\tpublic<\/span> static<\/span> int<\/span>[<\/span>]<\/span> mergeTwoSortedArrays<\/span>(<\/span>int<\/span>[<\/span>]<\/span> one,<\/span> int<\/span>[<\/span>]<\/span> two)<\/span> {<\/span>\r\n\t\tint<\/span>[<\/span>]<\/span> sorted =<\/span> new<\/span> int<\/span>[<\/span>one.<\/span>length +<\/span> two.<\/span>length]<\/span>;<\/span>\r\n\r\n\t\tint<\/span> i =<\/span> 0<\/span>;<\/span>\r\n\t\tint<\/span> j =<\/span> 0<\/span>;<\/span>\r\n\t\tint<\/span> k =<\/span> 0<\/span>;<\/span>\r\n\r\n\t\twhile<\/span> (<\/span>i <<\/span> one.<\/span>length &&<\/span> j <<\/span> two.<\/span>length)<\/span> {<\/span>\r\n\t\t\tif<\/span> (<\/span>one[<\/span>i]<\/span> <<\/span> two[<\/span>j]<\/span>)<\/span> {<\/span>\r\n\t\t\t\tsorted[<\/span>k]<\/span> =<\/span> one[<\/span>i]<\/span>;<\/span>\r\n\t\t\t\tk++<\/span>;<\/span>\r\n\t\t\t\ti++<\/span>;<\/span>\r\n\t\t\t}<\/span> else<\/span> {<\/span>\r\n\t\t\t\tsorted[<\/span>k]<\/span> =<\/span> two[<\/span>j]<\/span>;<\/span>\r\n\t\t\t\tk++<\/span>;<\/span>\r\n\t\t\t\tj++<\/span>;<\/span>\r\n\t\t\t}<\/span>\r\n\t\t}<\/span>\r\n\r\n\t\tif<\/span> (<\/span>i ==<\/span> one.<\/span>length)<\/span> {<\/span>\r\n\t\t\twhile<\/span> (<\/span>j <<\/span> two.<\/span>length)<\/span> {<\/span>\r\n\t\t\t\tsorted[<\/span>k]<\/span> =<\/span> two[<\/span>j]<\/span>;<\/span>\r\n\t\t\t\tk++<\/span>;<\/span>\r\n\t\t\t\tj++<\/span>;<\/span>\r\n\t\t\t}<\/span>\r\n\t\t}<\/span>\r\n\r\n\t\tif<\/span> (<\/span>j ==<\/span> two.<\/span>length)<\/span> {<\/span>\r\n\t\t\twhile<\/span> (<\/span>i <<\/span> one.<\/span>length)<\/span> {<\/span>\r\n\t\t\t\tsorted[<\/span>k]<\/span> =<\/span> one[<\/span>i]<\/span>;<\/span>\r\n\t\t\t\tk++<\/span>;<\/span>\r\n\t\t\t\ti++<\/span>;<\/span>\r\n\t\t\t}<\/span>\r\n\t\t}<\/span>\r\n\r\n\t\treturn<\/span> sorted;<\/span>\r\n\t}<\/span>\r\n\r\n\tpublic<\/span> static<\/span> int<\/span>[<\/span>]<\/span> mergeSort<\/span>(<\/span>int<\/span>[<\/span>]<\/span> arr,<\/span> int<\/span> lo,<\/span> int<\/span> hi)<\/span> {<\/span>\r\n\t\tif<\/span> (<\/span>lo ==<\/span> hi)<\/span> {<\/span>\r\n\t\t\tint<\/span>[<\/span>]<\/span> br =<\/span> new<\/span> int<\/span>[<\/span>1<\/span>]<\/span>;<\/span>\r\n\t\t\tbr[<\/span>0<\/span>]<\/span> =<\/span> arr[<\/span>lo]<\/span>;<\/span>\r\n\r\n\t\t\treturn<\/span> br;<\/span>\r\n\t\t}<\/span>\r\n\r\n\t\tint<\/span> mid =<\/span> (<\/span>lo +<\/span> hi)<\/span> \/<\/span> 2<\/span>;<\/span>\r\n\r\n\t\tint<\/span>[<\/span>]<\/span> fh =<\/span> mergeSort<\/span>(<\/span>arr,<\/span> lo,<\/span> mid)<\/span>;<\/span>\r\n\t\tint<\/span>[<\/span>]<\/span> sh =<\/span> mergeSort<\/span>(<\/span>arr,<\/span> mid +<\/span> 1<\/span>,<\/span> hi)<\/span>;<\/span>\r\n\r\n\t\tint<\/span>[<\/span>]<\/span> merged =<\/span> mergeTwoSortedArrays<\/span>(<\/span>fh,<\/span> sh)<\/span>;<\/span>\r\n\r\n\t\treturn<\/span> merged;<\/span>\r\n\t}<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u4f60\u80fd\u7528Java\u521b\u5efa\u4e00\u4e2a\u5b57\u7b26\u91d1\u5b57\u5854\u5417\uff1f<\/h2>\n
    \u6a21\u5f0f\u7a0b\u5e8f\u662f\u4e00\u4e2a\u975e\u5e38\u6d41\u884c\u7684\u9762\u8bd5\u9898\u76ee\u3002\u8fd9\u79cd\u7c7b\u578b\u7684\u95ee\u9898\u7528\u4e8e\u4e86\u89e3\u9762\u8bd5\u8005\u7684\u903b\u8f91\u601d\u7ef4\u80fd\u529b\u3002\u8bf7\u53c2\u8003Java\u4e2d\u7684\u91d1\u5b57\u5854\u6a21\u5f0f\u7a0b\u5e8f\u793a\u4f8b\uff0c\u4e86\u89e3\u521b\u5efa\u91d1\u5b57\u5854\u6a21\u5f0f\u7684\u4e0d\u540c\u65b9\u6cd5\u3002<\/p>\n
    17. \u7f16\u5199Java\u7a0b\u5e8f\uff0c\u68c0\u67e5\u4e24\u4e2a\u6570\u7ec4\u662f\u5426\u5305\u542b\u76f8\u540c\u7684\u5143\u7d20\u3002<\/h2>\n
    \u4e3a\u4e86\u68c0\u67e5\u4e24\u4e2a\u6570\u7ec4\u662f\u5426\u5305\u542b\u76f8\u540c\u7684\u5143\u7d20\uff0c\u4f60\u9700\u8981\u9996\u5148\u4ece\u8fd9\u4e24\u4e2a\u6570\u7ec4\u4e2d\u521b\u5efa\u4e00\u4e2a\u5143\u7d20\u96c6\u5408\uff0c\u7136\u540e\u6bd4\u8f83\u8fd9\u4e9b\u96c6\u5408\u4e2d\u7684\u5143\u7d20\uff0c\u4ee5\u786e\u5b9a\u662f\u5426\u5b58\u5728\u4e00\u4e2a\u5728\u4e24\u4e2a\u96c6\u5408\u4e2d\u90fd\u4e0d\u5b58\u5728\u7684\u5143\u7d20\u3002\u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u68c0\u67e5\u4e24\u4e2a\u6570\u7ec4\u662f\u5426\u53ea\u5305\u542b\u76f8\u540c\u7684\u5143\u7d20\uff1a<\/p>\n
    import<\/span> java.<\/span>util.<\/span><\/span>Arrays<\/span><\/span>;<\/span>\r\nimport<\/span> java.<\/span>util.<\/span><\/span>HashSet<\/span><\/span>;<\/span>\r\nimport<\/span> java.<\/span>util.<\/span><\/span>Set<\/span><\/span>;<\/span>\r\n\r\npublic<\/span> class<\/span> ArraySameElements<\/span> {<\/span>\r\n\r\n\tpublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>\r\n\t\tInteger<\/span>[<\/span>]<\/span> a1 =<\/span> {<\/span>1<\/span>,<\/span>2<\/span>,<\/span>3<\/span>,<\/span>2<\/span>,<\/span>1<\/span>}<\/span>;<\/span>\r\n\t\tInteger<\/span>[<\/span>]<\/span> a2 =<\/span> {<\/span>1<\/span>,<\/span>2<\/span>,<\/span>3<\/span>}<\/span>;<\/span>\r\n\t\tInteger<\/span>[<\/span>]<\/span> a3 =<\/span> {<\/span>1<\/span>,<\/span>2<\/span>,<\/span>3<\/span>,<\/span>4<\/span>}<\/span>;<\/span>\r\n\t\t\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>sameElements<\/span>(<\/span>a1,<\/span> a2)<\/span>)<\/span>;<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>sameElements<\/span>(<\/span>a1,<\/span> a3)<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n\tstatic<\/span> boolean<\/span> sameElements<\/span>(<\/span>Object<\/span>[<\/span>]<\/span> array1,<\/span> Object<\/span>[<\/span>]<\/span> array2)<\/span> {<\/span>\r\n\t\tSet<\/span><<\/span>Object<\/span>><\/span><\/span> uniqueElements1 =<\/span> new<\/span> HashSet<\/span><<\/span>><\/span><\/span>(<\/span>Arrays<\/span>.<\/span>asList<\/span>(<\/span>array1)<\/span>)<\/span>;<\/span>\r\n\t\tSet<\/span><<\/span>Object<\/span>><\/span><\/span> uniqueElements2 =<\/span> new<\/span> HashSet<\/span><<\/span>><\/span><\/span>(<\/span>Arrays<\/span>.<\/span>asList<\/span>(<\/span>array2)<\/span>)<\/span>;<\/span>\r\n\t\t\r\n\t\t\/\/ if size is different, means there will be a mismatch<\/span>\r\n\t\tif<\/span> (<\/span>uniqueElements1.<\/span>size<\/span>(<\/span>)<\/span> !=<\/span> uniqueElements2.<\/span>size<\/span>(<\/span>)<\/span>)<\/span> return<\/span> false<\/span>;<\/span>\r\n\t\t\r\n\t\tfor<\/span> (<\/span>Object<\/span> obj :<\/span> uniqueElements1)<\/span> {<\/span>\r\n\t\t\t\/\/ element not present in both?<\/span>\r\n\t\t\tif<\/span> (<\/span>!<\/span>uniqueElements2.<\/span>contains<\/span>(<\/span>obj)<\/span>)<\/span> return<\/span> false<\/span>;<\/span>\r\n\t\t}<\/span>\r\n\t\t\r\n\t\treturn<\/span> true<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
    \r\nOutput\r\n\r\ntrue false\r\n<\/code><\/pre>\n
    \u4f60\u600e\u4e48\u5728Java\u4e2d\u8ba1\u7b97\u6574\u6570\u6570\u7ec4\u4e2d\u6240\u6709\u5143\u7d20\u7684\u548c\uff1f<\/h2>\n
    \u4f60\u53ef\u4ee5\u4f7f\u7528\u4e00\u4e2afor\u5faa\u73af\u6765\u904d\u5386\u6570\u7ec4\u5143\u7d20\u5e76\u5c06\u5b83\u4eec\u76f8\u52a0\uff0c\u6700\u540e\u5f97\u5230\u603b\u548c\u3002<\/p>\n
    int<\/span>[<\/span>]<\/span> array =<\/span> {<\/span> 1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>,<\/span> 4<\/span>,<\/span> 5<\/span> }<\/span>;<\/span>\r\n\r\nint<\/span> sum =<\/span> 0<\/span>;<\/span>\r\n\r\nfor<\/span> (<\/span>int<\/span> i :<\/span> array)<\/span>\r\n\tsum +=<\/span> i;<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>sum)<\/span>;<\/span>\r\n<\/code><\/pre>\n
    19. \u5728Java\u4e2d\uff0c\u5982\u4f55\u627e\u5230\u6570\u7ec4\u4e2d\u7b2c\u4e8c\u5927\u7684\u6570\uff1f<\/h2>\n
    \u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u6709\u5f88\u591a\u65b9\u6cd5\u3002\u60a8\u53ef\u4ee5\u5c06\u6570\u7ec4\u6309\u81ea\u7136\u5347\u5e8f\u6392\u5e8f\u5e76\u53d6\u5012\u6570\u7b2c\u4e8c\u4e2a\u503c\u3002\u7136\u800c\uff0c\u6392\u5e8f\u662f\u4e00\u9879\u6602\u8d35\u7684\u64cd\u4f5c\u3002\u60a8\u4e5f\u53ef\u4ee5\u4f7f\u7528\u4e24\u4e2a\u53d8\u91cf\u5728\u5355\u6b21\u8fed\u4ee3\u4e2d\u627e\u5230\u7b2c\u4e8c\u5927\u7684\u503c\uff0c\u5982\u4e0b\u9762\u7684\u793a\u4f8b\u6240\u793a\u3002<\/p>\n
    private<\/span> static<\/span> int<\/span> findSecondHighest<\/span>(<\/span>int<\/span>[<\/span>]<\/span> array)<\/span> {<\/span>\r\n\tint<\/span> highest =<\/span> Integer<\/span>.<\/span>MIN_VALUE<\/span>;<\/span>\r\n\tint<\/span> secondHighest =<\/span> Integer<\/span>.<\/span>MIN_VALUE<\/span>;<\/span>\r\n\r\n\tfor<\/span> (<\/span>int<\/span> i :<\/span> array)<\/span> {<\/span>\r\n\t\tif<\/span> (<\/span>i ><\/span> highest)<\/span> {<\/span>\r\n\t\t\tsecondHighest =<\/span> highest;<\/span>\r\n\t\t\thighest =<\/span> i;<\/span>\r\n\t\t}<\/span> else<\/span> if<\/span> (<\/span>i ><\/span> secondHighest)<\/span> {<\/span>\r\n\t\t\tsecondHighest =<\/span> i;<\/span>\r\n\t\t}<\/span>\r\n\r\n\t}<\/span>\r\n\treturn<\/span> secondHighest;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u5728Java\u4e2d\u5982\u4f55\u5bf9\u6570\u7ec4\u8fdb\u884c\u6d17\u724c\uff1f<\/h2>\n
    \u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528Random\u7c7b\u751f\u6210\u968f\u673a\u7d22\u5f15\u53f7\u5e76\u5bf9\u5143\u7d20\u8fdb\u884c\u6d17\u724c\u3002<\/p>\n
    int<\/span>[<\/span>]<\/span> array =<\/span> {<\/span> 1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>,<\/span> 4<\/span>,<\/span> 5<\/span>,<\/span> 6<\/span>,<\/span> 7<\/span> }<\/span>;<\/span>\r\n\r\nRandom<\/span> rand =<\/span> new<\/span> Random<\/span>(<\/span>)<\/span>;<\/span>\r\n\r\nfor<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> array.<\/span>length;<\/span> i++<\/span>)<\/span> {<\/span>\r\n\tint<\/span> randomIndexToSwap =<\/span> rand.<\/span>nextInt<\/span>(<\/span>array.<\/span>length)<\/span>;<\/span>\r\n\tint<\/span> temp =<\/span> array[<\/span>randomIndexToSwap]<\/span>;<\/span>\r\n\tarray[<\/span>randomIndexToSwap]<\/span> =<\/span> array[<\/span>i]<\/span>;<\/span>\r\n\tarray[<\/span>i]<\/span> =<\/span> temp;<\/span>\r\n}<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>Arrays<\/span>.<\/span>toString<\/span>(<\/span>array)<\/span>)<\/span>;<\/span>\r\n<\/code><\/pre>\n
    \u4f60\u53ef\u4ee5\u5728\u53e6\u4e00\u4e2afor\u5faa\u73af\u5185\u8fd0\u884c\u6d17\u724c\u4ee3\u7801\uff0c\u4ee5\u8fdb\u884c\u591a\u8f6e\u6d17\u724c\u3002<\/p>\n
    21. \u5728Java\u4e2d\uff0c\u4f60\u5982\u4f55\u627e\u5230\u6587\u672c\u6587\u4ef6\u4e2d\u7684\u5b57\u7b26\u4e32\uff1f<\/h2>\n
    \u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528Scanner\u7c7b\u9010\u884c\u8bfb\u53d6\u6587\u4ef6\u5185\u5bb9\uff0c\u7136\u540e\u4f7f\u7528String\u7684contains()\u65b9\u6cd5\u6765\u68c0\u67e5\u5b57\u7b26\u4e32\u662f\u5426\u5b58\u5728\u4e8e\u6587\u4ef6\u4e2d\u3002<\/p>\n
    boolean<\/span> findStringInFile<\/span>(<\/span>String<\/span> filePath,<\/span> String<\/span> str)<\/span> throws<\/span> FileNotFoundException<\/span> {<\/span>\r\n\tFile<\/span> file =<\/span> new<\/span> File<\/span>(<\/span>filePath)<\/span>;<\/span>\r\n\r\n\tScanner<\/span> scanner =<\/span> new<\/span> Scanner<\/span>(<\/span>file)<\/span>;<\/span>\r\n\r\n\t\/\/ read the file line by line<\/span>\r\n\twhile<\/span> (<\/span>scanner.<\/span>hasNextLine<\/span>(<\/span>)<\/span>)<\/span> {<\/span>\r\n\t\tString<\/span> line =<\/span> scanner.<\/span>nextLine<\/span>(<\/span>)<\/span>;<\/span>\r\n\t\tif<\/span> (<\/span>line.<\/span>contains<\/span>(<\/span>str)<\/span>)<\/span> {<\/span>\r\n\t\t\tscanner.<\/span>close<\/span>(<\/span>)<\/span>;<\/span>\r\n\t\t\treturn<\/span> true<\/span>;<\/span>\r\n\t\t}<\/span>\r\n\t}<\/span>\r\n\tscanner.<\/span>close<\/span>(<\/span>)<\/span>;<\/span>\r\n\r\n\treturn<\/span> false<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u8bf7\u6ce8\u610f\uff0c\u793a\u4f8b\u4ee3\u7801\u5047\u8bbe\u8981\u5728\u6587\u4ef6\u4e2d\u641c\u7d22\u7684\u5b57\u7b26\u4e32\u4e0d\u5305\u542b\u6362\u884c\u7b26\u3002<\/p>\n
    \u5728Java\u4e2d\uff0c\u4f60\u5982\u4f55\u4ee5\u7279\u5b9a\u7684\u683c\u5f0f\u6253\u5370\u65e5\u671f\uff1f<\/h2>\n
    \u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528SimpleDateFormat\u7c7b\u6765\u683c\u5f0f\u5316\u65e5\u671f\u5b57\u7b26\u4e32\u3002<\/p>\n
    String<\/span> pattern =<\/span> \"MM-dd-yyyy\"<\/span>;<\/span>\r\nSimpleDateFormat<\/span> simpleDateFormat =<\/span> new<\/span> SimpleDateFormat<\/span>(<\/span>pattern)<\/span>;<\/span>\r\n\r\nString<\/span> date =<\/span> simpleDateFormat.<\/span>format<\/span>(<\/span>new<\/span> Date<\/span>(<\/span>)<\/span>)<\/span>;<\/span>\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>date)<\/span>;<\/span> \/\/ 06-23-2020<\/span>\r\n<\/code><\/pre>\n
    \u4e86\u89e3\u66f4\u591a\u5173\u4e8eJava\u7684SimpleDateFormat\u3002<\/p>\n
    23. \u5728Java\u4e2d\u5982\u4f55\u5408\u5e76\u4e24\u4e2a\u5217\u8868\uff1f<\/h2>\n
    \u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u5728Java\u4e2d\u4f7f\u7528addAll()\u65b9\u6cd5\u5c06\u591a\u4e2a\u5217\u8868\u5408\u5e76\u3002<\/p>\n
    List<\/span><<\/span>String<\/span>><\/span><\/span> list1 =<\/span> new<\/span> ArrayList<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>\r\nlist1.<\/span>add<\/span>(<\/span>\"1\"<\/span>)<\/span>;<\/span>\r\nList<\/span><<\/span>String<\/span>><\/span><\/span> list2 =<\/span> new<\/span> ArrayList<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>\r\nlist2.<\/span>add<\/span>(<\/span>\"2\"<\/span>)<\/span>;<\/span>\r\n\r\nList<\/span><<\/span>String<\/span>><\/span><\/span> mergedList =<\/span> new<\/span> ArrayList<\/span><<\/span>><\/span><\/span>(<\/span>list1)<\/span>;<\/span>\r\nmergedList.<\/span>addAll<\/span>(<\/span>list2)<\/span>;<\/span>\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>mergedList)<\/span>;<\/span> \/\/ [1, 2]<\/span>\r\n<\/code><\/pre>\n
    \u7f16\u5199\u4e00\u4e2aJava\u7a0b\u5e8f\uff0c\u6839\u636e\u503c\u5bf9HashMap\u8fdb\u884c\u6392\u5e8f\u3002<\/h2>\n
    HashMap\u4e0d\u662f\u4e00\u4e2a\u6709\u5e8f\u7684\u96c6\u5408\u3002\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u6839\u636e\u503c\u5bf9\u6761\u76ee\u8fdb\u884c\u6392\u5e8f\u5e76\u5c06\u5b83\u4eec\u5b58\u50a8\u5230LinkedHashMap\u4e2d\uff0c\u8be5\u6570\u636e\u7ed3\u6784\u4fdd\u6301\u63d2\u5165\u7684\u987a\u5e8f\u3002<\/p>\n
    import<\/span> java.<\/span>util.<\/span><\/span>ArrayList<\/span><\/span>;<\/span>\r\nimport<\/span> java.<\/span>util.<\/span><\/span>HashMap<\/span><\/span>;<\/span>\r\nimport<\/span> java.<\/span>util.<\/span><\/span>LinkedHashMap<\/span><\/span>;<\/span>\r\nimport<\/span> java.<\/span>util.<\/span><\/span>List<\/span><\/span>;<\/span>\r\nimport<\/span> java.<\/span>util.<\/span><\/span>Map<\/span><\/span>;<\/span>\r\nimport<\/span> java.<\/span>util.<\/span><\/span>Map<\/span>.<\/span>Entry<\/span><\/span>;<\/span>\r\nimport<\/span> java.<\/span>util.<\/span><\/span>Set<\/span><\/span>;<\/span>\r\n\r\npublic<\/span> class<\/span> SortHashMapByValue<\/span> {<\/span>\r\n\r\n\tpublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>\r\n\t\tMap<\/span><<\/span>String<\/span>,<\/span> Integer<\/span>><\/span><\/span> scores =<\/span> new<\/span> HashMap<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>\r\n\r\n\t\tscores.<\/span>put<\/span>(<\/span>\"David\"<\/span>,<\/span> 95<\/span>)<\/span>;<\/span>\r\n\t\tscores.<\/span>put<\/span>(<\/span>\"Jane\"<\/span>,<\/span> 80<\/span>)<\/span>;<\/span>\r\n\t\tscores.<\/span>put<\/span>(<\/span>\"Mary\"<\/span>,<\/span> 97<\/span>)<\/span>;<\/span>\r\n\t\tscores.<\/span>put<\/span>(<\/span>\"Lisa\"<\/span>,<\/span> 78<\/span>)<\/span>;<\/span>\r\n\t\tscores.<\/span>put<\/span>(<\/span>\"Dino\"<\/span>,<\/span> 65<\/span>)<\/span>;<\/span>\r\n\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>scores)<\/span>;<\/span>\r\n\r\n\t\tscores =<\/span> sortByValue<\/span>(<\/span>scores)<\/span>;<\/span>\r\n\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>scores)<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n\tprivate<\/span> static<\/span> Map<\/span><<\/span>String<\/span>,<\/span> Integer<\/span>><\/span><\/span> sortByValue<\/span>(<\/span>Map<\/span><<\/span>String<\/span>,<\/span> Integer<\/span>><\/span><\/span> scores)<\/span> {<\/span>\r\n\t\tMap<\/span><<\/span>String<\/span>,<\/span> Integer<\/span>><\/span><\/span> sortedByValue =<\/span> new<\/span> LinkedHashMap<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>\r\n\r\n\t\t\/\/ get the entry set<\/span>\r\n\t\tSet<\/span><<\/span>Entry<\/span><<\/span>String<\/span>,<\/span> Integer<\/span>><\/span>><\/span><\/span> entrySet =<\/span> scores.<\/span>entrySet<\/span>(<\/span>)<\/span>;<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>entrySet)<\/span>;<\/span>\r\n\r\n\t\t\/\/ create a list since the set is unordered<\/span>\r\n\t\tList<\/span><<\/span>Entry<\/span><<\/span>String<\/span>,<\/span> Integer<\/span>><\/span>><\/span><\/span> entryList =<\/span> new<\/span> ArrayList<\/span><<\/span>><\/span><\/span>(<\/span>entrySet)<\/span>;<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>entryList)<\/span>;<\/span>\r\n\r\n\t\t\/\/ sort the list by value<\/span>\r\n\t\tentryList.<\/span>sort<\/span>(<\/span>(<\/span>x,<\/span> y)<\/span> -><\/span> x.<\/span>getValue<\/span>(<\/span>)<\/span>.<\/span>compareTo<\/span>(<\/span>y.<\/span>getValue<\/span>(<\/span>)<\/span>)<\/span>)<\/span>;<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>entryList)<\/span>;<\/span>\r\n\r\n\t\t\/\/ populate the new hash map<\/span>\r\n\t\tfor<\/span> (<\/span>Entry<\/span><<\/span>String<\/span>,<\/span> Integer<\/span>><\/span><\/span> e :<\/span> entryList)<\/span>\r\n\t\t\tsortedByValue.<\/span>put<\/span>(<\/span>e.<\/span>getKey<\/span>(<\/span>)<\/span>,<\/span> e.<\/span>getValue<\/span>(<\/span>)<\/span>)<\/span>;<\/span>\r\n\r\n\t\treturn<\/span> sortedByValue;<\/span>\r\n\t}<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
    25. \u5728Java\u4e2d\uff0c\u5982\u4f55\u4ece\u8f93\u5165\u7684\u5b57\u7b26\u4e32\u4e2d\u79fb\u9664\u6240\u6709\u7ed9\u5b9a\u5b57\u7b26\u7684\u51fa\u73b0\uff1f<\/h2>\n
    String\u7c7b\u6ca1\u6709\u5220\u9664\u5b57\u7b26\u7684\u65b9\u6cd5\u3002\u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528replace()\u65b9\u6cd5\u521b\u5efa\u4e00\u4e2a\u4e0d\u542b\u6709\u6307\u5b9a\u5b57\u7b26\u7684\u65b0\u5b57\u7b26\u4e32\uff1a<\/p>\n
    String<\/span> str1 =<\/span> \"abcdABCDabcdABCD\"<\/span>;<\/span>\r\n\t\t\r\nstr1 =<\/span> str1.<\/span>replace<\/span>(<\/span>\"a\"<\/span>,<\/span> \"\"<\/span>)<\/span>;<\/span> \r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>str1)<\/span>;<\/span> \/\/ bcdABCDbcdABCD<\/span>\r\n<\/code><\/pre>\n
    \u5728Java\u4e2d\uff0cString\u662f\u4e0d\u53ef\u53d8\u7684\u3002\u6240\u6709\u7684\u5b57\u7b26\u4e32\u64cd\u4f5c\u65b9\u6cd5\u90fd\u4f1a\u8fd4\u56de\u4e00\u4e2a\u65b0\u7684\u5b57\u7b26\u4e32\uff0c\u6240\u4ee5\u4f60\u9700\u8981\u5c06\u5176\u8d4b\u503c\u7ed9\u53e6\u4e00\u4e2a\u53d8\u91cf\u3002\u4e86\u89e3\u66f4\u591a\u5173\u4e8e\u5728Java\u4e2d\u4ece\u5b57\u7b26\u4e32\u4e2d\u5220\u9664\u5b57\u7b26\u7684\u65b9\u6cd5\u3002<\/p>\n
    \u5728Java\u4e2d\uff0c\u600e\u6837\u83b7\u53d6\u5b57\u7b26\u4e32\u4e2d\u4e0d\u540c\u5b57\u7b26\u53ca\u5176\u6570\u91cf\uff1f<\/h2>\n
    \u4f60\u53ef\u4ee5\u4ece\u5b57\u7b26\u4e32\u4e2d\u521b\u5efa\u5b57\u7b26\u6570\u7ec4\u3002\u7136\u540e\u904d\u5386\u5b57\u7b26\u6570\u7ec4\uff0c\u5e76\u6839\u636e\u5b57\u7b26\u521b\u5efa\u4e00\u4e2aHashMap\uff0c\u5176\u4e2d\u5b57\u7b26\u4f5c\u4e3a\u952e\uff0c\u5176\u51fa\u73b0\u6b21\u6570\u4f5c\u4e3a\u503c\u3002\u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u63d0\u53d6\u5b57\u7b26\u4e32\u4e2d\u7684\u5b57\u7b26\u5e76\u8ba1\u6570\uff1a<\/p>\n
    String<\/span> str1 =<\/span> \"abcdABCDabcd\"<\/span>;<\/span>\r\n\r\nchar<\/span>[<\/span>]<\/span> chars =<\/span> str1.<\/span>toCharArray<\/span>(<\/span>)<\/span>;<\/span>\r\n\r\nMap<\/span><<\/span>Character<\/span>,<\/span> Integer<\/span>><\/span><\/span> charsCount =<\/span> new<\/span> HashMap<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>\r\n\r\nfor<\/span> (<\/span>char<\/span> c :<\/span> chars)<\/span> {<\/span>\r\n\tif<\/span> (<\/span>charsCount.<\/span>containsKey<\/span>(<\/span>c)<\/span>)<\/span> {<\/span>\r\n\t\tcharsCount.<\/span>put<\/span>(<\/span>c,<\/span> charsCount.<\/span>get<\/span>(<\/span>c)<\/span> +<\/span> 1<\/span>)<\/span>;<\/span>\r\n\t}<\/span> else<\/span>\r\n\t\tcharsCount.<\/span>put<\/span>(<\/span>c,<\/span> 1<\/span>)<\/span>;<\/span>\r\n}<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>charsCount)<\/span>;<\/span> \/\/ {a=2, A=1, b=2, B=1, c=2, C=1, d=2, D=1}<\/span>\r\n<\/code><\/pre>\n
    27. \u4f60\u80fd\u901a\u8fc7\u7a0b\u5e8f\u6765\u8bc1\u660eJava\u4e2d\u7684String\u5bf9\u8c61\u662f\u4e0d\u53ef\u53d8\u7684\u5417\uff1f<\/h2>\n
    \u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u8bc1\u660e\u4e00\u4e2aString\u5bf9\u8c61\u662f\u4e0d\u53ef\u53d8\u7684\uff0c\u4ee3\u7801\u4e2d\u7684\u6ce8\u91ca\u89e3\u91ca\u4e86\u6bcf\u4e2a\u6b65\u9aa4\u7684\u542b\u4e49\u3002<\/p>\n
    String<\/span> s1 =<\/span> \"Java\"<\/span>;<\/span> \/\/ \"Java\" String created in pool and reference assigned to s1<\/span>\r\n\r\nString<\/span> s2 =<\/span> s1;<\/span> \/\/s2 also has the same reference to \"Java\" in the pool<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s1 ==<\/span> s2)<\/span>;<\/span> \/\/ proof that s1 and s2 have the same reference<\/span>\r\n\r\ns1 =<\/span> \"Python\"<\/span>;<\/span> \r\n\/\/s1 value got changed above, so how String is immutable?<\/span>\r\n\r\n\/\/in the above case a new String \"Python\" got created in the pool<\/span>\r\n\/\/s1 is now referring to the new String in the pool <\/span>\r\n\/\/BUT, the original String \"Java\" is still unchanged and remains in the pool<\/span>\r\n\/\/s2 is still referring to the original String \"Java\" in the pool<\/span>\r\n\r\n\/\/ proof that s1 and s2 have different reference<\/span>\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s1 ==<\/span> s2)<\/span>;<\/span> \r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s2)<\/span>;<\/span> \r\n\/\/ prints \"Java\" supporting the fact that original String value is unchanged, hence String is immutable<\/span>\r\n<\/code><\/pre>\n
    \u4f60\u53ef\u4ee5\u5199\u4e00\u4e9bJava\u4ee3\u7801\u6765\u5c55\u793a\u7ee7\u627f\u5417\uff1f<\/h2>\n
    \u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528 extends \u5173\u952e\u5b57\u521b\u5efa Animal \u7c7b\u7684\u5b50\u7c7b\u3002\u65b0\u5efa\u7684 Cat \u7c7b\u7ee7\u627f\u4e86 Animal \u7c7b\u7684\u53d8\u91cf\uff0c\u5e76\u6dfb\u52a0\u4e86\u4e00\u4e9b\u4ec5\u5c5e\u4e8e Cat \u7c7b\u7684\u4ee3\u7801\u3002<\/p>\n
    class<\/span> Animal<\/span> {<\/span>\r\n\tString<\/span> color;<\/span>\r\n}<\/span>\r\n\r\nclass<\/span> Cat<\/span> extends<\/span> Animal<\/span> {<\/span>\r\n\tvoid<\/span> meow<\/span>(<\/span>)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"Meow\"<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u4f60\u5982\u4f55\u5728Java\u4e2d\u5c55\u793a\u591a\u91cd\u7ee7\u627f\u7684\u83f1\u5f62\u95ee\u9898\uff1f<\/h2>\n
    \u94bb\u77f3\u95ee\u9898\u53d1\u751f\u5728\u4e00\u4e2a\u7c7b\u4ece\u591a\u4e2a\u7c7b\u7ee7\u627f\uff0c\u5e76\u4e14\u5f53\u4e0d\u6e05\u695a\u8981\u6267\u884c\u6765\u81ea\u54ea\u4e2a\u7c7b\u7684\u65b9\u6cd5\u65f6\uff0c\u4f1a\u4ea7\u751f\u6b67\u4e49\u3002\u4e3a\u4e86\u907f\u514d\u94bb\u77f3\u95ee\u9898\uff0c\u5728Java\u4e2d\u4e0d\u5141\u8bb8\u591a\u91cd\u7ee7\u627f\uff0c\u4ee5\u4e0b\u793a\u4f8b\u8bf4\u660e\u4e86\u8fd9\u4e2a\u95ee\u9898\u3002<\/p>\n
    interface<\/span> I<\/span> {<\/span>\r\n\tvoid<\/span> foo<\/span>(<\/span>)<\/span>;<\/span>\r\n}<\/span>\r\nclass<\/span> A<\/span> implements<\/span> I<\/span> {<\/span>\r\n\tpublic<\/span> void<\/span> foo<\/span>(<\/span>)<\/span> {<\/span>}<\/span>\r\n}<\/span>\r\n\r\nclass<\/span> B<\/span> implements<\/span> I<\/span> {<\/span>\r\n\tpublic<\/span> void<\/span> foo<\/span>(<\/span>)<\/span> {<\/span>}<\/span>\r\n}<\/span>\r\n\r\nclass<\/span> C<\/span> extends<\/span> A<\/span>,<\/span> B<\/span> {<\/span> \/\/ won't compile<\/span>\r\n\tpublic<\/span> void<\/span> bar<\/span>(<\/span>)<\/span> {<\/span>\r\n\t\tsuper<\/span>.<\/span>foo<\/span>(<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u4f60\u5982\u4f55\u5728Java\u4e2d\u8bf4\u660e\u4e00\u4e2atry catch\u7684\u4f8b\u5b50\uff1f<\/h2>\n
    \u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86try-catch\u7684\u4f8b\u5b50\u3002<\/p>\n
    try<\/span> {<\/span>\r\n\tFileInputStream<\/span> fis =<\/span> new<\/span> FileInputStream<\/span>(<\/span>\"test.txt\"<\/span>)<\/span>;<\/span>\r\n}<\/span> catch<\/span>(<\/span>FileNotFoundException<\/span> e)<\/span> {<\/span>\r\n\te.<\/span>printStackTrace<\/span>(<\/span>)<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u4ece Java 7 \u5f00\u59cb\uff0c\u4f60\u8fd8\u53ef\u4ee5\u5728\u4e00\u4e2a catch \u5757\u4e2d\u6355\u83b7\u591a\u4e2a\u5f02\u5e38\uff0c\u5982\u4e0b\u4f8b\u6240\u793a\u3002\u5f53\u4f60\u5728\u6240\u6709\u7684 catch \u5757\u4e2d\u6709\u76f8\u540c\u7684\u4ee3\u7801\u65f6\uff0c\u8fd9\u5c06\u975e\u5e38\u6709\u7528\u3002<\/p>\n
    public<\/span> static<\/span> void<\/span> foo<\/span>(<\/span>int<\/span> x)<\/span> throws<\/span> IllegalArgumentException<\/span>,<\/span> NullPointerException<\/span> {<\/span>\r\n\t\/\/ some code<\/span>\r\n}<\/span>\r\n\r\npublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>\r\n\ttry<\/span> {<\/span>\r\n\t\tfoo<\/span>(<\/span>10<\/span>)<\/span>;<\/span>\r\n\t}<\/span> catch<\/span> (<\/span>IllegalArgumentException<\/span> |<\/span> NullPointerException<\/span> e)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>e.<\/span>getMessage<\/span>(<\/span>)<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u5199\u4e00\u4e2aJava\u7a0b\u5e8f\u6765\u5c55\u793a\u4e00\u4e2a\u7a7a\u6307\u9488\u5f02\u5e38\u3002<\/h2>\n
    \u5982\u679c\u60a8\u5728\u7a7a\uff08null\uff09\u4e0a\u8c03\u7528\u51fd\u6570\uff0c\u5b83\u4f1a\u5f15\u53d1\u7a7a\u6307\u9488\u5f02\u5e38\uff0c\u5c31\u50cf\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u6240\u793a\u3002<\/p>\n
    public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>\r\n\tprintString<\/span>(<\/span>null<\/span>,<\/span> 3<\/span>)<\/span>;<\/span>\r\n\t\r\n}<\/span>\r\n\r\nstatic<\/span> void<\/span> printString<\/span>(<\/span>String<\/span> s,<\/span> int<\/span> count)<\/span> {<\/span>\r\n\tfor<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> count;<\/span> i++<\/span>)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s.<\/span>toUpperCase<\/span>(<\/span>)<\/span>)<\/span>;<\/span> \/\/ Exception in thread \"main\" java.lang.NullPointerException<\/span>\r\n\t}<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u5728\u65e9\u671f\u9a8c\u8bc1\u4e2d\uff0c\u4f60\u5e94\u8be5\u8fdb\u884c\u7a7a\u503c\u68c0\u67e5\uff0c\u5c31\u50cf\u4e0b\u9762\u8fd9\u4e2a\u793a\u4f8b\u4ee3\u7801\u4e2d\u6240\u793a\u3002<\/p>\n
    static<\/span> void<\/span> printString<\/span>(<\/span>String<\/span> s,<\/span> int<\/span> count)<\/span> {<\/span>\r\n\tif<\/span> (<\/span>s ==<\/span> null<\/span>)<\/span> return<\/span>;<\/span>\r\n\tfor<\/span> (<\/span>int<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> count;<\/span> i++<\/span>)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s.<\/span>toUpperCase<\/span>(<\/span>)<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u6839\u636e\u9879\u76ee\u8981\u6c42\uff0c\u60a8\u8fd8\u53ef\u4ee5\u6839\u636e\u53c2\u6570\u629b\u51faIllegalArgumentException\u3002<\/p>\n
    \u4f60\u5982\u4f55\u5728Java\u4e2d\u521b\u5efa\u8bb0\u5f55\uff1f<\/h2>\n
    \u5728Java 16\u4e2d\uff0c\u8bb0\u5f55\uff08Records\uff09\u88ab\u6dfb\u52a0\u4e3a\u6807\u51c6\u529f\u80fd\u3002\u4f7f\u7528\u8bb0\u5f55\u53ef\u4ee5\u4ec5\u9700\u5c11\u91cf\u4ee3\u7801\u521b\u5efa\u4e00\u4e2aPOJO\u7c7b\u3002\u8bb0\u5f55\u4f1a\u81ea\u52a8\u751f\u6210hashCode()\u3001equals()\u3001getter\u65b9\u6cd5\u548ctoString()\u65b9\u6cd5\u7684\u4ee3\u7801\u3002\u8bb0\u5f55\u662ffinal\u7684\uff0c\u5e76\u4e14\u4f1a\u9690\u5f0f\u7ee7\u627fjava.lang.Record\u7c7b\u3002\u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u4e00\u79cd\u521b\u5efa\u8bb0\u5f55\u7684\u65b9\u6cd5\uff1a<\/p>\n
    import<\/span> java.<\/span>util.<\/span><\/span>Map<\/span><\/span>;<\/span>\r\n \r\npublic<\/span> record<\/span> EmpRecord<\/span>(<\/span>int<\/span> id,<\/span> String<\/span> name,<\/span> long<\/span> salary,<\/span> Map<\/span><<\/span>String<\/span>,<\/span> String<\/span>><\/span><\/span> addresses)<\/span> {<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u4e86\u89e3\u6709\u5173Java\u4e2d\u7684\u8bb0\u5f55\u7684\u66f4\u591a\u4fe1\u606f\u3002\u6709\u5173POJO\u7684\u8be6\u7ec6\u4fe1\u606f\uff0c\u8bf7\u53c2\u9605\u7ef4\u57fa\u767e\u79d1\u4e0a\u7684Plain old Java \u5bf9\u8c61\u3002<\/p>\n
    \u5728Java\u4e2d\u5982\u4f55\u521b\u5efa\u6587\u672c\u5757\uff1f<\/h2>\n
    Java 15\u589e\u52a0\u4e86\u6587\u672c\u5757\u529f\u80fd\u3002\u60a8\u53ef\u4ee5\u4f7f\u7528\u6587\u672c\u5757\u521b\u5efa\u591a\u884c\u5b57\u7b26\u4e32\u3002\u591a\u884c\u5b57\u7b26\u4e32\u5fc5\u987b\u5199\u5728\u4e00\u5bf9\u4e09\u53cc\u5f15\u53f7\u5185\uff0c\u5982\u4ee5\u4e0b\u793a\u4f8b\u6240\u793a\uff1a<\/p>\n
    String<\/span> textBlock =<\/span> \"\"\"\r\n\t\tHi\r\n\t\tHello\r\n\t\tYes\"\"\"<\/span>;<\/span>\r\n<\/code><\/pre>\n
    \u4e0e\u521b\u5efa\u5b57\u7b26\u76f8\u540c\uff0c\u4f8b\u5982Hi\\\\nHello\\\\nYes\u3002<\/p>\n
    \u8bf7\u5728Java\u4e2d\u5c55\u793a\u4f7f\u7528\u5f00\u5173\u8868\u8fbe\u5f0f\u548c\u591a\u6807\u7b7e(case)\u8bed\u53e5\u7684\u793a\u4f8b\u3002<\/h2>\n
    \u5728Java 14\u4e2d\uff0c\u5f00\u5173\u8868\u8fbe\u5f0f\u88ab\u6dfb\u52a0\u4e3a\u6807\u51c6\u529f\u80fd\u3002\u4ee5\u4e0b\u793a\u4f8b\u5c55\u793a\u4e86\u5f00\u5173\u8868\u8fbe\u5f0f\u4ee5\u53ca\u591a\u6807\u7b7ecase\u8bed\u53e5\u3002<\/p>\n
    int<\/span> choice =<\/span> 2<\/span>;<\/span>\r\n\r\nint<\/span> x =<\/span> switch<\/span> (<\/span>choice)<\/span> {<\/span>\r\n    case<\/span> 1<\/span>,<\/span> 2<\/span>,<\/span> 3<\/span>:<\/span>\r\n\t    yield<\/span> choice;<\/span>\r\n    default<\/span>:<\/span>\r\n\t    yield<\/span> -<\/span>1<\/span>;<\/span>\r\n}<\/span>;<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"x = \"<\/span> +<\/span> x)<\/span>;<\/span> \/\/ x = 2<\/span>\r\n<\/code><\/pre>\n
    \u4f60\u4e5f\u53ef\u4ee5\u5728switch\u8868\u8fbe\u5f0f\u4e2d\u4f7f\u7528lambda\u8868\u8fbe\u5f0f\u3002<\/p>\n
    String<\/span> day =<\/span> \"TH\"<\/span>;<\/span>\r\nString<\/span> result =<\/span> switch<\/span> (<\/span>day)<\/span> {<\/span>\r\n    case<\/span> \"M\"<\/span>,<\/span> \"W\"<\/span>,<\/span> \"F\"<\/span> -><\/span> \"MWF\"<\/span>;<\/span>\r\n    case<\/span> \"T\"<\/span>,<\/span> \"TH\"<\/span>,<\/span> \"S\"<\/span> -><\/span> \"TTS\"<\/span>;<\/span>\r\n\r\n    default<\/span> -><\/span> {<\/span>\r\n\t    if<\/span> (<\/span>day.<\/span>isEmpty<\/span>(<\/span>)<\/span>)<\/span>\r\n\t\t    yield<\/span> \"Please insert a valid day.\"<\/span>;<\/span>\r\n\t    else<\/span>\r\n\t\t    yield<\/span> \"Looks like a Sunday.\"<\/span>;<\/span>\r\n    }<\/span>\r\n}<\/span>;<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>result)<\/span>;<\/span> \/\/ TTH<\/span>\r\n<\/code><\/pre>\n
    35. \u4ece\u547d\u4ee4\u884c\u4e2d\u5982\u4f55\u7f16\u8bd1\u548c\u8fd0\u884cJava\u7c7b\uff1f<\/h2>\n
    \u8fd9\u4e2a\u4f8b\u5b50\u6307\u7684\u662f\u4e0b\u9762\u7684Java\u6587\u4ef6\uff1a<\/p>\n
    public<\/span> class<\/span> Test<\/span> {<\/span>\r\n\r\npublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span> args[<\/span>]<\/span>)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"Hi\"<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
    \u60a8\u53ef\u4ee5\u5728\u7ec8\u7aef\u4e2d\u4f7f\u7528\u4ee5\u4e0b\u547d\u4ee4\u8fdb\u884c\u7f16\u8bd1\u3002<\/p>\n
    \r\n
      \r\n \t
    1. javac Test.java<\/li>\r\n<\/ol>\r\n<\/code><\/pre>\n
      \u8981\u8fd0\u884c\u8fd9\u4e2a\u7c7b\uff0c\u8bf7\u5728\u4f60\u7684\u7ec8\u7aef\u4e2d\u4f7f\u7528\u4ee5\u4e0b\u547d\u4ee4\uff1a<\/p>\n
      \r\n
        \r\n \t
      1. java<\/span> Test<\/li>\r\n<\/ol>\r\n<\/code><\/pre>\n
        \u6700\u8fd1\u7684\u7248\u672c\u4e2d\uff0c\u5982\u679c\u7c7b\u6587\u4ef6\u4e0d\u5b58\u5728\uff0cJava\u547d\u4ee4\u4e5f\u4f1a\u7f16\u8bd1\u7a0b\u5e8f\u3002\u5982\u679c\u7c7b\u5728\u4e00\u4e2a\u5305\u4e2d\uff0c\u6bd4\u5982com.example\uff0c\u90a3\u4e48\u5b83\u5e94\u8be5\u5728com\/example\u6587\u4ef6\u5939\u4e2d\u3002\u7f16\u8bd1\u548c\u8fd0\u884c\u7684\u547d\u4ee4\u662f\uff1a<\/p>\n
        \r\n
          \r\n \t
        1. java<\/span> com\/example\/Test.java<\/li>\r\n<\/ol>\r\n<\/code><\/pre>\n
          \u5982\u679c\u4f60\u7684\u8bfe\u7a0b\u9700\u8981\u4e00\u4e9b\u989d\u5916\u7684JAR\u6587\u4ef6\u6765\u7f16\u8bd1\u548c\u8fd0\u884c\uff0c\u4f60\u53ef\u4ee5\u4f7f\u7528java -cp\u9009\u9879\u3002\u4f8b\u5982\uff1a<\/p>\n
          \r\n
            \r\n \t
          1. java<\/span> -cp<\/span> .:~\/.m2\/repository\/log4j\/log4j\/1.2.17\/log4j-1.2.17.jar com\/example\/Test.java<\/li>\r\n<\/ol>\r\n<\/code><\/pre>\n
            \u5728Java\u4e2d\uff0c\u4f60\u5982\u4f55\u521b\u5efa\u4e00\u4e2a\u679a\u4e3e\uff1f<\/h2>\n
            \u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u521b\u5efa\u4e00\u4e2a\u57fa\u672c\u7684\u679a\u4e3e\u7c7b\u578b\uff1a<\/p>\n
            public<\/span> enum<\/span> ThreadStates<\/span> {<\/span>\r\n\tSTART<\/span>,<\/span>\r\n\tRUNNING<\/span>,<\/span>\r\n\tWAITING<\/span>,<\/span>\r\n\tDEAD<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
            ThreadStates\u662f\u4e00\u4e2a\u679a\u4e3e\uff0c\u5176\u4e2d\u5305\u542b\u56fa\u5b9a\u7684\u5e38\u91cf\u5b57\u6bb5START\u3001RUNNING\u3001WAITING\u548cDEAD\u3002\u6240\u6709\u679a\u4e3e\u90fd\u9690\u5f0f\u5730\u6269\u5c55\u4e86java.lang.Enum\u7c7b\uff0c\u5e76\u5b9e\u73b0\u4e86Serializable\u548cComparable\u63a5\u53e3\u3002\u679a\u4e3e\u4e5f\u53ef\u4ee5\u6709\u65b9\u6cd5\u3002\u4e86\u89e3\u66f4\u591a\u5173\u4e8eJava\u4e2d\u7684\u679a\u4e3e\u7684\u77e5\u8bc6\u3002<\/p>\n
            37. \u5982\u4f55\u5728 Java \u4e2d\u4f7f\u7528forEach()\u65b9\u6cd5\uff1f<\/h2>\n
            The forEach() \u65b9\u6cd5\u4e3a\u8fed\u4ee3\u5bf9\u8c61\u7684\u6240\u6709\u5143\u7d20\u63d0\u4f9b\u4e86\u4e00\u4e2a\u5feb\u6377\u65b9\u5f0f\u6765\u6267\u884c\u64cd\u4f5c\u3002\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u6f14\u793a\u4e86\u5982\u4f55\u904d\u5386\u5217\u8868\u5143\u7d20\u5e76\u6253\u5370\u5b83\u4eec\u3002<\/p>\n
            List<\/span><<\/span>String<\/span>><\/span><\/span> list =<\/span> new<\/span> ArrayList<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>\r\n\r\nIterator<\/span><<\/span>String<\/span>><\/span><\/span> it =<\/span> list.<\/span>iterator<\/span>(<\/span>)<\/span>;<\/span>\r\n\r\nwhile<\/span> (<\/span>it.<\/span>hasNext<\/span>(<\/span>)<\/span>)<\/span> {<\/span>\r\n\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>it.<\/span>next<\/span>(<\/span>)<\/span>)<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
            \u4f60\u53ef\u4ee5\u4f7f\u7528lambda\u8868\u8fbe\u5f0f\u5728forEach()\u65b9\u6cd5\u4e2d\u6765\u7f29\u5c0f\u4ee3\u7801\u7684\u5927\u5c0f\uff0c\u5982\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u6240\u793a\u3002<\/p>\n
            List<\/span><<\/span>String<\/span>><\/span><\/span> list =<\/span> new<\/span> ArrayList<\/span><<\/span>><\/span><\/span>(<\/span>)<\/span>;<\/span>\r\n\r\nlist.<\/span>forEach<\/span>(<\/span>System<\/span>.<\/span>out::<\/span>print<\/span>)<\/span>;<\/span>\r\n<\/code><\/pre>\n
            \u5982\u4f55\u7f16\u5199\u5177\u6709\u9ed8\u8ba4\u548c\u9759\u6001\u65b9\u6cd5\u7684\u63a5\u53e3\uff1f<\/h2>\n
            Java 8\u5728\u63a5\u53e3\u4e2d\u5f15\u5165\u4e86\u9ed8\u8ba4\u65b9\u6cd5\u548c\u9759\u6001\u65b9\u6cd5\uff0c\u8fd9\u6837\u586b\u8865\u4e86\u63a5\u53e3\u548c\u62bd\u8c61\u7c7b\u4e4b\u95f4\u7684\u5dee\u8ddd\u3002\u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u4e00\u79cd\u4f7f\u7528\u9ed8\u8ba4\u65b9\u6cd5\u548c\u9759\u6001\u65b9\u6cd5\u7f16\u5199\u63a5\u53e3\u7684\u65b9\u5f0f\u3002<\/p>\n
            public<\/span> interface<\/span> Interface1<\/span> {<\/span>\r\n\t\r\n\t\/\/ regular abstract method<\/span>\r\n\tvoid<\/span> method1<\/span>(<\/span>String<\/span> str)<\/span>;<\/span>\r\n\t\r\n\tdefault<\/span> void<\/span> log<\/span>(<\/span>String<\/span> str)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"I1 logging::\"<\/span> +<\/span> str)<\/span>;<\/span>\r\n\t}<\/span>\r\n\t\r\n\tstatic<\/span> boolean<\/span> isNull<\/span>(<\/span>String<\/span> str)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"Interface Null Check\"<\/span>)<\/span>;<\/span>\r\n\r\n\t\treturn<\/span> str ==<\/span> null<\/span> ?<\/span> true<\/span> :<\/span> \"\"<\/span>.<\/span>equals<\/span>(<\/span>str)<\/span> ?<\/span> true<\/span> :<\/span> false<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
            \u5728Java 8\u7684\u63a5\u53e3\u66f4\u6539\u4e2d\uff0c\u6df1\u5165\u4e86\u89e3\u63a5\u53e3\u4e2d\u7684\u9ed8\u8ba4\u65b9\u6cd5\u548c\u9759\u6001\u65b9\u6cd5\u3002<\/p>\n
            39. \u4f60\u5982\u4f55\u521b\u5efa\u4e00\u4e2a\u529f\u80fd\u6027\u63a5\u53e3\uff1f<\/h2>\n
            \u4e00\u4e2a\u53ea\u6709\u4e00\u4e2a\u62bd\u8c61\u65b9\u6cd5\u7684\u63a5\u53e3\u88ab\u79f0\u4e3a\u51fd\u6570\u5f0f\u63a5\u53e3\u3002\u51fd\u6570\u5f0f\u63a5\u53e3\u7684\u4e3b\u8981\u4f18\u52bf\u662f\u53ef\u4ee5\u4f7f\u7528lambda\u8868\u8fbe\u5f0f\u6765\u5b9e\u4f8b\u5316\u5b83\u4eec\uff0c\u907f\u514d\u4f7f\u7528\u81c3\u80bf\u7684\u533f\u540d\u7c7b\u5b9e\u73b0\u3002@FunctionalInterface\u6ce8\u89e3\u8868\u793a\u4e00\u4e2a\u51fd\u6570\u5f0f\u63a5\u53e3\uff0c\u5982\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u6240\u793a\uff1a<\/p>\n
            @FunctionalInterface<\/span>\r\ninterface<\/span> Foo<\/span> {<\/span>\r\n\tvoid<\/span> test<\/span>(<\/span>)<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
            \u8bf7\u5c55\u793a\u4e00\u4e2a\u5728Java\u4e2d\u4f7f\u7528lambda\u8868\u8fbe\u5f0f\u7684\u4f8b\u5b50\u3002<\/h2>\n
            Runnable\u662f\u51fd\u6570\u5f0f\u63a5\u53e3\u7684\u4e00\u4e2a\u5f88\u597d\u7684\u4f8b\u5b50\u3002\u60a8\u53ef\u4ee5\u4f7f\u7528lambda\u8868\u8fbe\u5f0f\u6765\u521b\u5efa\u4e00\u4e2a\u53ef\u8fd0\u884c\u7684\u5b9e\u4f8b\uff0c\u5982\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u6240\u793a\uff1a<\/p>\n
            Runnable<\/span> r1 =<\/span> (<\/span>)<\/span> -><\/span> System<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"My Runnable\"<\/span>)<\/span>;<\/span>\r\n<\/code><\/pre>\n
            \u7ed9\u51faJava\u4e2d\u91cd\u8f7d\u548c\u91cd\u5199\u7684\u793a\u4f8b\u3002<\/h2>\n
            \u5f53\u4e00\u4e2a\u7c7b\u6709\u4e24\u4e2a\u6216\u66f4\u591a\u7684\u65b9\u6cd5\u62e5\u6709\u76f8\u540c\u7684\u540d\u79f0\u65f6\uff0c\u5b83\u4eec\u88ab\u79f0\u4e3a\u91cd\u8f7d\u65b9\u6cd5\u3002\u4e0b\u9762\u7684\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u4e00\u4e2a\u88ab\u79f0\u4e3aprint\u7684\u91cd\u8f7d\u65b9\u6cd5\u3002<\/p>\n
            class<\/span> Foo<\/span> {<\/span>\r\n\tvoid<\/span> print<\/span>(<\/span>String<\/span> s)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s)<\/span>;<\/span>\r\n\t}<\/span>\r\n\r\n\tvoid<\/span> print<\/span>(<\/span>String<\/span> s,<\/span> int<\/span> count)<\/span> {<\/span>\r\n\t\twhile<\/span> (<\/span>count ><\/span> 0<\/span>)<\/span> {<\/span>\r\n\t\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s)<\/span>;<\/span>\r\n\t\t\tcount--<\/span>;<\/span>\r\n\t\t}<\/span>\r\n\t}<\/span>\r\n\r\n}<\/span>\r\n<\/code><\/pre>\n
            \u5f53\u5728\u5b50\u7c7b\u4e2d\u5b9e\u73b0\u4e86\u8d85\u7c7b\u65b9\u6cd5\u65f6\uff0c\u8fd9\u88ab\u79f0\u4e3a\u8986\u76d6\u3002\u4ee5\u4e0b\u793a\u4f8b\u4ee3\u7801\u5c55\u793a\u4e86\u5982\u4f55\u5bf9\u5728\u4e24\u4e2a\u7c7b\u4e2d\u5b9e\u73b0\u7684printname()\u65b9\u6cd5\u8fdb\u884c\u6ce8\u91ca\u3002<\/p>\n
            class<\/span> Base<\/span> {<\/span>\r\n\tvoid<\/span> printName<\/span>(<\/span>)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"Base Class\"<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n}<\/span>\r\n\r\nclass<\/span> Child<\/span> extends<\/span> Base<\/span> {<\/span>\r\n\t@Override<\/span>\r\n\tvoid<\/span> printName<\/span>(<\/span>)<\/span> {<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"Child Class\"<\/span>)<\/span>;<\/span>\r\n\t}<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
            \u4e86\u89e3Java\u4e2d\u7684\u8986\u76d6\uff08overriding\uff09\u548c\u91cd\u8f7d\uff08overloading\uff09\u3002<\/p>\n
            42. Can you predict what will be produced?
            \n43. What do you think will be the outcome?
            \n44. Can you guess the resulting output?
            \n45. What do you expect the output to be?
            \n46. Can you anticipate the output that will be generated?
            \n47. What do you suppose will be the produced result?
            \n48. Can you hypothesize the output that will be produced?
            \n49. What do you anticipate the resulting output will be?<\/h2>\n
            \u901a\u8fc7\u731c\u6d4b\u4ee5\u4e0b\u4ee3\u7801\u7247\u6bb5\u7684\u8f93\u51fa\u6765\u6d4b\u8bd5\u4f60\u81ea\u5df1\u7684\u80fd\u529b\u3002<\/p>\n
            \n
            String<\/span> s1 =<\/span> \"abc\"<\/span>;<\/span>\r\nString<\/span> s2 =<\/span> \"abc\"<\/span>;<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"s1 == s2 is:\"<\/span> +<\/span> s1 ==<\/span> s2)<\/span>;<\/span>\r\n<\/code><\/pre>\n
            \u8f93\u51fa
            \n\u9519\u8bef\u7ed9\u5b9a\u8bed\u53e5\u7684\u8f93\u51fa\u662f\u9519\u8bef\u7684\uff0c\u56e0\u4e3a+\u8fd0\u7b97\u7b26\u7684\u4f18\u5148\u7ea7\u9ad8\u4e8e==\u8fd0\u7b97\u7b26\u3002\u6240\u4ee5\u7ed9\u5b9a\u7684\u8868\u8fbe\u5f0f\u88ab\u8ba1\u7b97\u4e3a\u201cs1 == s2\u662f\uff1aabc\u201d == \u201cabc\u201d\uff0c\u8fd9\u662f\u9519\u8bef\u7684\u3002<\/p>\n<\/details>\n
            \n
            String<\/span> s3 =<\/span> \"JournalDev\"<\/span>;<\/span>\r\nint<\/span> start =<\/span> 1<\/span>;<\/span>\r\nchar<\/span> end =<\/span> 5<\/span>;<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s3.<\/span>substring<\/span>(<\/span>start,<\/span> end)<\/span>)<\/span>;<\/span>\r\n<\/code><\/pre>\n
            \u8f93\u51fa
            \nourn\u7ed9\u5b9a\u8bed\u53e5\u7684\u8f93\u51fa\u662fourn\u3002\u9996\u5b57\u7b26\u81ea\u52a8\u8f6c\u6362\u4e3a\u6574\u6570\u3002\u7136\u540e\uff0c\u7531\u4e8e\u9996\u5b57\u7b26\u7d22\u5f15\u4e3a0\uff0c\u5b83\u4f1a\u4eceo\u5f00\u59cb\u6253\u5370\u76f4\u5230n\u3002\u8bf7\u6ce8\u610f\uff0cString\u7684\u5b50\u5b57\u7b26\u4e32\u65b9\u6cd5\u521b\u5efa\u4e00\u4e2a\u4ecestart\u7d22\u5f15\u5f00\u59cb\u5e76\u5ef6\u4f38\u5230end-1\u7d22\u5f15\u5904\u7684\u5b50\u5b57\u7b26\u4e32\u3002<\/p>\n<\/details>\n
            \n
            HashSet<\/span> shortSet =<\/span> new<\/span> HashSet<\/span>(<\/span>)<\/span>;<\/span>\r\n\r\n\tfor<\/span> (<\/span>short<\/span> i =<\/span> 0<\/span>;<\/span> i <<\/span> 100<\/span>;<\/span> i++<\/span>)<\/span> {<\/span>\r\n    shortSet.<\/span>add<\/span>(<\/span>i)<\/span>;<\/span>\r\n    shortSet.<\/span>remove<\/span>(<\/span>i -<\/span> 1<\/span>)<\/span>;<\/span>\r\n}<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>shortSet.<\/span>size<\/span>(<\/span>)<\/span>)<\/span>;<\/span>\r\n<\/code><\/pre>\n
            \u8f93\u51fa
            \n100shortSet\u7684\u5927\u5c0f\u4e3a100\u3002Java\u4e2d\u7684\u81ea\u52a8\u88c5\u7bb1\u529f\u80fd\u610f\u5473\u7740\u5177\u6709\u539f\u59cb\u7c7b\u578bshort\u7684\u8868\u8fbe\u5f0fi\u5c06\u88ab\u8f6c\u6362\u4e3aShort\u5bf9\u8c61\u3002\u540c\u6837\uff0c\u5177\u6709\u539f\u59cb\u7c7b\u578bint\u7684\u8868\u8fbe\u5f0fi – 1\u5c06\u88ab\u81ea\u52a8\u88c5\u7bb1\u4e3a\u4e00\u4e2aInteger\u5bf9\u8c61\u3002\u7531\u4e8eHashSet\u4e2d\u6ca1\u6709Integer\u5bf9\u8c61\uff0c\u6240\u4ee5\u6ca1\u6709\u4efb\u4f55\u4e1c\u897f\u88ab\u79fb\u9664\uff0c\u5927\u5c0f\u4ecd\u7136\u662f100\u3002<\/p>\n<\/details>\n
            \n
            try<\/span> {<\/span>\r\n\tif<\/span> (<\/span>flag)<\/span> {<\/span>\r\n  \t\twhile<\/span> (<\/span>true<\/span>)<\/span> {<\/span>\r\n   \t\t}<\/span>\r\n   \t}<\/span> else<\/span> {<\/span>\r\n   \t\tSystem<\/span>.<\/span>exit<\/span>(<\/span>1<\/span>)<\/span>;<\/span>\r\n   \t}<\/span>\r\n}<\/span> finally<\/span> {<\/span>\r\n   \tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>\"In Finally\"<\/span>)<\/span>;<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
            \u8f93\u51fa
            \n\u6ca1\u6709\u8f93\u51fa\u3002\u5982\u679c\u6807\u5fd7\u4f4d\u4e3a\u771f\uff0c\u8fd9\u6bb5\u4ee3\u7801\u4f1a\u5bfc\u81f4\u4e00\u4e2a\u65e0\u9650\u5faa\u73af\uff1b\u5982\u679c\u6807\u5fd7\u4f4d\u4e3a\u5047\uff0c\u7a0b\u5e8f\u4f1a\u9000\u51fa\u3002\u6700\u7ec8\u5757\u5c06\u6c38\u8fdc\u4e0d\u4f1a\u6267\u884c\u3002<\/details>\n
            \n
            String<\/span> str =<\/span> null<\/span>;<\/span>\r\nString<\/span> str1=<\/span>\"abc\"<\/span>;<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>str1.<\/span>equals<\/span>(<\/span>\"abc\"<\/span>)<\/span> |<\/span> str.<\/span>equals<\/span>(<\/span>null<\/span>)<\/span>)<\/span>;<\/span>\r\n<\/code><\/pre>\n
            \u8f93\u51fa
            \n\u4e3b\u7ebf\u7a0b\u4e2d\u7684\u5f02\u5e38\uff1ajava.lang.NullPointerException\uff1a\u65e0\u6cd5\u8c03\u7528”String.equals(Object)”\uff0c\u56e0\u4e3a””\u4e3a\u7a7a\u7ed9\u5b9a\u7684\u6253\u5370\u8bed\u53e5\u5c06\u4f1a\u629b\u51fajava.lang.NullPointerException\u5f02\u5e38\uff0c\u56e0\u4e3a\u903b\u8f91\u6216\u8fd0\u7b97\u7b26\u5728\u8fd4\u56de\u7ed3\u679c\u4e4b\u524d\u4f1a\u8bc4\u4f30\u4e24\u4e2a\u6587\u5b57\u3002\u7531\u4e8estr\u4e3a\u7a7a\uff0c.equals()\u65b9\u6cd5\u5c06\u629b\u51fa\u5f02\u5e38\u3002\u603b\u662f\u5efa\u8bae\u4f7f\u7528\u77ed\u8def\u903b\u8f91\u8fd0\u7b97\u7b26\uff0c\u5982||\u548c&&\uff0c\u5b83\u4eec\u4f1a\u4ece\u5de6\u5230\u53f3\u8bc4\u4f30\u6587\u5b57\u503c\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u7531\u4e8e\u7b2c\u4e00\u4e2a\u6587\u5b57\u5c06\u8fd4\u56detrue\uff0c\u5b83\u5c06\u8df3\u8fc7\u5bf9\u7b2c\u4e8c\u4e2a\u6587\u5b57\u7684\u8bc4\u4f30\u3002<\/p>\n<\/details>\n
            \n
            String<\/span> x =<\/span> \"abc\"<\/span>;<\/span>\r\nString<\/span> y =<\/span> \"abc\"<\/span>;<\/span>\r\n\r\nx.<\/span>concat<\/span>(<\/span>y)<\/span>;<\/span>\r\n\r\nSystem<\/span>.<\/span>out.<\/span>print<\/span>(<\/span>x)<\/span>;<\/span>\r\n<\/code><\/pre>\n
            \u8f93\u51fa
            \nabcx.concat(y)\u521b\u5efa\u4e86\u4e00\u4e2a\u65b0\u5b57\u7b26\u4e32\uff0c\u4f46\u672a\u88ab\u8d4b\u503c\u7ed9x\uff0c\u6240\u4ee5x\u7684\u503c\u6ca1\u6709\u6539\u53d8\u3002<\/p>\n<\/details>\n
            \n
            public<\/span> class<\/span> MathTest<\/span> {<\/span>\r\n\r\n \tpublic<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>  \t\t\r\n   \t\tint<\/span> x =<\/span> 10<\/span> *<\/span> 10<\/span> -<\/span> 10<\/span>;<\/span>\r\n   \t\t\r\n   \t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>x)<\/span>;<\/span>\r\n   \t}<\/span>\r\n   \r\n}<\/span>\r\n<\/code><\/pre>\n
            \u9519\u8bef\uff1a\u7c7bMathTest\u4e2d\u7684\u4e3b\u65b9\u6cd5\u4e0d\u662f\u9759\u6001\u7684\uff0c\u8bf7\u5c06\u4e3b\u65b9\u6cd5\u5b9a\u4e49\u4e3a\uff1a
            \npublic static void main(String[] args)\u5c3d\u7ba1\u770b\u8d77\u6765\u8fd9\u4e2a\u95ee\u9898\u4f3c\u4e4e\u6d89\u53ca\u6570\u5b66\u8fd0\u7b97\u7b26\u7684\u6267\u884c\u987a\u5e8f\uff0c\u4f46\u95ee\u9898\u5b9e\u9645\u4e0a\u5728\u4e8e\u6ce8\u610f\u5230\u4e3b\u65b9\u6cd5\u6ca1\u6709\u88ab\u58f0\u660e\u4e3a\u9759\u6001\u7684\u3002<\/p>\n<\/details>\n
            \n
            public<\/span> class<\/span> Test<\/span> {<\/span>\r\n   \r\n  \tpublic<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>]<\/span> args)<\/span> {<\/span>\r\n   \t\ttry<\/span> {<\/span>\r\n   \t\t\tthrow<\/span> new<\/span> IOException<\/span>(<\/span>\"Hello\"<\/span>)<\/span>;<\/span>\r\n   \t\t}<\/span> catch<\/span>(<\/span>IOException<\/span> |<\/span> Exception<\/span> e)<\/span> {<\/span>\r\n   \t\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>e.<\/span>getMessage<\/span>(<\/span>)<\/span>)<\/span>;<\/span>\r\n   \t\t}<\/span>\r\n   \t}<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
            \u8fd9\u6bb5\u4ee3\u7801\u5728\u7f16\u8bd1\u65f6\u51fa\u73b0\u9519\u8bef\u3002IOException\u5f02\u5e38\u5df2\u7ecf\u88ab\u66ff\u4ee3\u7684Exception\u6355\u83b7\u3002<\/details>\n
            \u627e\u51fa\u4ee5\u4e0b\u4ee3\u7801\u7247\u6bb5\u4e2d\u76845\u4e2a\u9519\u8bef\u3002<\/h2>\n
            Note: Chinese translations may vary depending on the context and specific technical terms used in the code snippet.<\/p>\n
            package<\/span> com.<\/span>digitalocean.<\/span>programming<\/span>-<\/span>interviews;<\/span>\r\n\r\npublic<\/span> class<\/span> String<\/span> Programs<\/span> {<\/span>\r\n\r\n\tstatic<\/span> void<\/span> main<\/span>(<\/span>String<\/span>[<\/span>10<\/span>]<\/span> args)<\/span> {<\/span>\r\n\t\tString<\/span> s =<\/span> \"abc\"<\/span>\r\n\t\tSystem<\/span>.<\/span>out.<\/span>println<\/span>(<\/span>s)<\/span>;<\/span>\r\n\t}<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
            \u7b54\u6848\u5305\u540d\u4e0d\u80fd\u6709\u8fde\u5b57\u7b26\u3002
            \n\u7c7b\u540d\u4e0d\u80fd\u6709\u7a7a\u683c\u3002
            \nmain\u65b9\u6cd5\u4e0d\u662fpublic\uff0c\u6240\u4ee5\u65e0\u6cd5\u8fd0\u884c\u3002
            \nmain\u65b9\u6cd5\u7684\u53c2\u6570\u4e0d\u5e94\u8be5\u6307\u5b9a\u5927\u5c0f\u3002
            \n\u5b57\u7b26\u4e32\u5b9a\u4e49\u4e2d\u7f3a\u5c11\u5206\u53f7\u3002<\/p>\n<\/details>\n
            \u7ed3\u8bba<\/h2>\n
            \u8fd9\u4e2a\u6536\u96c6\u4e8650\u4e2aJava\u7f16\u7a0b\u9762\u8bd5\u9898\u7684\u5408\u96c6\uff0c\u6db5\u76d6\u4e86\u4ece\u521d\u5b66\u8005\u5230\u4e13\u5bb6\u7ea7\u522b\u7684\u95ee\u9898\uff0c\u4ee5\u5e2e\u52a9\u4f60\u4e3a\u9762\u8bd5\u505a\u597d\u51c6\u5907\u3002<\/p>\n
            \u63a8\u8350\u9605\u8bfb\uff1a<\/p>\n
              \n
            • Java Tricky Interview Questions<\/li>\n
            • Java String Interview Questions<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"
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