{"id":18838,"date":"2024-03-15T17:42:17","date_gmt":"2024-03-15T17:42:17","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/what-are-the-different-ways-to-traverse-a-hashmap\/"},"modified":"2024-03-21T14:15:57","modified_gmt":"2024-03-21T14:15:57","slug":"what-are-the-different-ways-to-traverse-a-hashmap","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/what-are-the-different-ways-to-traverse-a-hashmap\/","title":{"rendered":"What are the different ways to traverse a hashmap?"},"content":{"rendered":"<p>There are several ways to iterate through a HashMap.<\/p>\n<ol>\n<li>Iterating using Iterator: by using the keySet() or entrySet() methods of a HashMap to obtain a set of keys or a set of key-value pairs, and then iterating through them using an Iterator.<\/li>\n<\/ol>\n<pre class=\"post-pre\"><code>HashMap&lt;String, Integer&gt; map = <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-title class_\">HashMap<\/span>&lt;&gt;();\r\n<span class=\"hljs-comment\">\/\/ \u6dfb\u52a0\u952e\u503c\u5bf9\u5230map<\/span>\r\n\r\n<span class=\"hljs-comment\">\/\/ \u904d\u5386\u952e\u96c6\u5408<\/span>\r\nIterator&lt;String&gt; iterator = map.keySet().iterator();\r\n<span class=\"hljs-keyword\">while<\/span> (iterator.hasNext()) {\r\n    <span class=\"hljs-type\">String<\/span> <span class=\"hljs-variable\">key<\/span> <span class=\"hljs-operator\">=<\/span> iterator.next();\r\n    <span class=\"hljs-comment\">\/\/ \u6839\u636ekey\u83b7\u53d6\u5bf9\u5e94\u7684\u503c<\/span>\r\n    <span class=\"hljs-type\">Integer<\/span> <span class=\"hljs-variable\">value<\/span> <span class=\"hljs-operator\">=<\/span> map.get(key);\r\n    <span class=\"hljs-comment\">\/\/ \u8fdb\u884c\u5176\u4ed6\u64cd\u4f5c<\/span>\r\n}\r\n\r\n<span class=\"hljs-comment\">\/\/ \u904d\u5386\u952e\u503c\u5bf9\u96c6\u5408<\/span>\r\nIterator&lt;Map.Entry&lt;String, Integer&gt;&gt; iterator = map.entrySet().iterator();\r\n<span class=\"hljs-keyword\">while<\/span> (iterator.hasNext()) {\r\n    Map.Entry&lt;String, Integer&gt; entry = iterator.next();\r\n    <span class=\"hljs-type\">String<\/span> <span class=\"hljs-variable\">key<\/span> <span class=\"hljs-operator\">=<\/span> entry.getKey();\r\n    <span class=\"hljs-type\">Integer<\/span> <span class=\"hljs-variable\">value<\/span> <span class=\"hljs-operator\">=<\/span> entry.getValue();\r\n    <span class=\"hljs-comment\">\/\/ \u8fdb\u884c\u5176\u4ed6\u64cd\u4f5c<\/span>\r\n}\r\n<\/code><\/pre>\n<ol>\n<li>Iterate through a key set or key-value pair set using foreach:<\/li>\n<\/ol>\n<pre class=\"post-pre\"><code>HashMap&lt;String, Integer&gt; map = <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-title class_\">HashMap<\/span>&lt;&gt;();\r\n<span class=\"hljs-comment\">\/\/ \u6dfb\u52a0\u952e\u503c\u5bf9\u5230map<\/span>\r\n\r\n<span class=\"hljs-comment\">\/\/ \u904d\u5386\u952e\u96c6\u5408<\/span>\r\n<span class=\"hljs-keyword\">for<\/span> (String key : map.keySet()) {\r\n    <span class=\"hljs-comment\">\/\/ \u6839\u636ekey\u83b7\u53d6\u5bf9\u5e94\u7684\u503c<\/span>\r\n    <span class=\"hljs-type\">Integer<\/span> <span class=\"hljs-variable\">value<\/span> <span class=\"hljs-operator\">=<\/span> map.get(key);\r\n    <span class=\"hljs-comment\">\/\/ \u8fdb\u884c\u5176\u4ed6\u64cd\u4f5c<\/span>\r\n}\r\n\r\n<span class=\"hljs-comment\">\/\/ \u904d\u5386\u952e\u503c\u5bf9\u96c6\u5408<\/span>\r\n<span class=\"hljs-keyword\">for<\/span> (Map.Entry&lt;String, Integer&gt; entry : map.entrySet()) {\r\n    <span class=\"hljs-type\">String<\/span> <span class=\"hljs-variable\">key<\/span> <span class=\"hljs-operator\">=<\/span> entry.getKey();\r\n    <span class=\"hljs-type\">Integer<\/span> <span class=\"hljs-variable\">value<\/span> <span class=\"hljs-operator\">=<\/span> entry.getValue();\r\n    <span class=\"hljs-comment\">\/\/ \u8fdb\u884c\u5176\u4ed6\u64cd\u4f5c<\/span>\r\n}\r\n<\/code><\/pre>\n<ol>\n<li>Traverse using Java 8&#8217;s Stream API:<\/li>\n<\/ol>\n<pre class=\"post-pre\"><code>HashMap&lt;String, Integer&gt; map = <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-title class_\">HashMap<\/span>&lt;&gt;();\r\n<span class=\"hljs-comment\">\/\/ \u6dfb\u52a0\u952e\u503c\u5bf9\u5230map<\/span>\r\n\r\n<span class=\"hljs-comment\">\/\/ \u904d\u5386\u952e\u96c6\u5408<\/span>\r\nmap.keySet().stream().forEach(key -&gt; {\r\n    <span class=\"hljs-comment\">\/\/ \u6839\u636ekey\u83b7\u53d6\u5bf9\u5e94\u7684\u503c<\/span>\r\n    <span class=\"hljs-type\">Integer<\/span> <span class=\"hljs-variable\">value<\/span> <span class=\"hljs-operator\">=<\/span> map.get(key);\r\n    <span class=\"hljs-comment\">\/\/ \u8fdb\u884c\u5176\u4ed6\u64cd\u4f5c<\/span>\r\n});\r\n\r\n<span class=\"hljs-comment\">\/\/ \u904d\u5386\u952e\u503c\u5bf9\u96c6\u5408<\/span>\r\nmap.entrySet().stream().forEach(entry -&gt; {\r\n    <span class=\"hljs-type\">String<\/span> <span class=\"hljs-variable\">key<\/span> <span class=\"hljs-operator\">=<\/span> entry.getKey();\r\n    <span class=\"hljs-type\">Integer<\/span> <span class=\"hljs-variable\">value<\/span> <span class=\"hljs-operator\">=<\/span> entry.getValue();\r\n    <span class=\"hljs-comment\">\/\/ \u8fdb\u884c\u5176\u4ed6\u64cd\u4f5c<\/span>\r\n});\r\n<\/code><\/pre>\n<p>Note: When deleting elements during traversal using Iterator or foreach, make sure to use the remove() method of the Iterator to avoid throwing a ConcurrentModificationException.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>There are several ways to iterate through a HashMap. Iterating using Iterator: by using the keySet() or entrySet() methods of a HashMap to obtain a set of keys or a set of key-value pairs, and then iterating through them using an Iterator. HashMap&lt;String, Integer&gt; map = new HashMap&lt;&gt;(); \/\/ \u6dfb\u52a0\u952e\u503c\u5bf9\u5230map \/\/ \u904d\u5386\u952e\u96c6\u5408 Iterator&lt;String&gt; iterator = [&hellip;]<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-18838","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"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>What are the different ways to traverse a hashmap? - Blog - Silicon Cloud<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.silicloud.com\/blog\/what-are-the-different-ways-to-traverse-a-hashmap\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"What are the different ways to traverse a hashmap?\" \/>\n<meta property=\"og:description\" content=\"There are several ways to iterate through a HashMap. Iterating using Iterator: by using the keySet() or entrySet() methods of a HashMap to obtain a set of keys or a set of key-value pairs, and then iterating through them using an Iterator. HashMap&lt;String, Integer&gt; map = new HashMap&lt;&gt;(); \/\/ \u6dfb\u52a0\u952e\u503c\u5bf9\u5230map \/\/ \u904d\u5386\u952e\u96c6\u5408 Iterator&lt;String&gt; iterator = [&hellip;]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.silicloud.com\/blog\/what-are-the-different-ways-to-traverse-a-hashmap\/\" \/>\n<meta property=\"og:site_name\" content=\"Blog - Silicon Cloud\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/SiliCloudGlobal\/\" \/>\n<meta property=\"article:published_time\" content=\"2024-03-15T17:42:17+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2024-03-21T14:15:57+00:00\" \/>\n<meta name=\"author\" content=\"Benjamin Taylor\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@SiliCloudGlobal\" \/>\n<meta name=\"twitter:site\" content=\"@SiliCloudGlobal\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Benjamin Taylor\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/what-are-the-different-ways-to-traverse-a-hashmap\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/what-are-the-different-ways-to-traverse-a-hashmap\/\"},\"author\":{\"name\":\"Benjamin Taylor\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/#\/schema\/person\/ac801fe9549a25960ce48aa2e0a691c9\"},\"headline\":\"What are the different ways to traverse a hashmap?\",\"datePublished\":\"2024-03-15T17:42:17+00:00\",\"dateModified\":\"2024-03-21T14:15:57+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/what-are-the-different-ways-to-traverse-a-hashmap\/\"},\"wordCount\":93,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\/\/www.silicloud.com\/blog\/#organization\"},\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.silicloud.com\/blog\/what-are-the-different-ways-to-traverse-a-hashmap\/\",\"url\":\"https:\/\/www.silicloud.com\/blog\/what-are-the-different-ways-to-traverse-a-hashmap\/\",\"name\":\"What are the different ways to traverse a hashmap? 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