{"id":13670,"date":"2024-03-15T07:34:48","date_gmt":"2024-03-15T07:34:48","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-to-use-java-regular-expressions-to-determine-if-it-is-a-number\/"},"modified":"2025-08-05T21:49:36","modified_gmt":"2025-08-05T21:49:36","slug":"how-to-use-java-regular-expressions-to-determine-if-it-is-a-number","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-to-use-java-regular-expressions-to-determine-if-it-is-a-number\/","title":{"rendered":"Java Regex to Check if String is Number"},"content":{"rendered":"<p>You can use Java regular expressions to check if a string is a number. Here is an example code:<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">import<\/span> java.util.regex.Pattern;\r\n\r\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title class_\">Main<\/span> {\r\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">static<\/span> <span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title function_\">main<\/span><span class=\"hljs-params\">(String[] args)<\/span> {\r\n        <span class=\"hljs-type\">String<\/span> <span class=\"hljs-variable\">str1<\/span> <span class=\"hljs-operator\">=<\/span> <span class=\"hljs-string\">\"12345\"<\/span>; <span class=\"hljs-comment\">\/\/ \u6570\u5b57<\/span>\r\n        <span class=\"hljs-type\">String<\/span> <span class=\"hljs-variable\">str2<\/span> <span class=\"hljs-operator\">=<\/span> <span class=\"hljs-string\">\"12.34\"<\/span>; <span class=\"hljs-comment\">\/\/ \u5c0f\u6570<\/span>\r\n        <span class=\"hljs-type\">String<\/span> <span class=\"hljs-variable\">str3<\/span> <span class=\"hljs-operator\">=<\/span> <span class=\"hljs-string\">\"abc123\"<\/span>; <span class=\"hljs-comment\">\/\/ \u5305\u542b\u5b57\u6bcd<\/span>\r\n        <span class=\"hljs-type\">String<\/span> <span class=\"hljs-variable\">str4<\/span> <span class=\"hljs-operator\">=<\/span> <span class=\"hljs-string\">\"12a34\"<\/span>; <span class=\"hljs-comment\">\/\/ \u5305\u542b\u975e\u6570\u5b57\u5b57\u7b26<\/span>\r\n\r\n        System.out.println(isNumeric(str1)); <span class=\"hljs-comment\">\/\/ true<\/span>\r\n        System.out.println(isNumeric(str2)); <span class=\"hljs-comment\">\/\/ true<\/span>\r\n        System.out.println(isNumeric(str3)); <span class=\"hljs-comment\">\/\/ false<\/span>\r\n        System.out.println(isNumeric(str4)); <span class=\"hljs-comment\">\/\/ false<\/span>\r\n    }\r\n\r\n    <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">static<\/span> <span class=\"hljs-type\">boolean<\/span> <span class=\"hljs-title function_\">isNumeric<\/span><span class=\"hljs-params\">(String str)<\/span> {\r\n        <span class=\"hljs-type\">Pattern<\/span> <span class=\"hljs-variable\">pattern<\/span> <span class=\"hljs-operator\">=<\/span> Pattern.compile(<span class=\"hljs-string\">\"-?\\\\d+(\\\\.\\\\d+)?\"<\/span>); <span class=\"hljs-comment\">\/\/ \u6570\u5b57\u7684\u6b63\u5219\u8868\u8fbe\u5f0f<\/span>\r\n        <span class=\"hljs-keyword\">return<\/span> pattern.matcher(str).matches();\r\n    }\r\n}\r\n<\/code><\/pre>\n<p>In the code above, the isNumeric method takes a string parameter and uses a regular expression to determine if the string is a number. The regular expression -?\\d+(\\.\\d+)? represents an optional negative sign, followed by one or more digits, and optionally followed by a decimal point and one or more digits. The Pattern.compile method is used to create a pattern for the regular expression, then the matcher method is used to apply this pattern to the string. Finally, the matches method is used to determine if the string matches the pattern, returning true if it does and false if it doesn&#8217;t.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>You can use Java regular expressions to check if a string is a number. Here is an example code: import java.util.regex.Pattern; public class Main { public static void main(String[] args) { String str1 = &#8220;12345&#8221;; \/\/ \u6570\u5b57 String str2 = &#8220;12.34&#8221;; \/\/ \u5c0f\u6570 String str3 = &#8220;abc123&#8221;; \/\/ \u5305\u542b\u5b57\u6bcd String str4 = &#8220;12a34&#8221;; \/\/ \u5305\u542b\u975e\u6570\u5b57\u5b57\u7b26 [&hellip;]<\/p>\n","protected":false},"author":11,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[1],"tags":[1990,9346,1992,1803,8466],"class_list":["post-13670","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-java-regex","tag-number-validation","tag-pattern-matching","tag-regular-expressions","tag-string-validation"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.5 (Yoast SEO v21.5) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Java Regex to Check if String is Number - Blog - Silicon Cloud<\/title>\n<meta name=\"description\" content=\"Learn how to use Java regular expressions to validate if a string is a number. 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