{"id":18835,"date":"2024-03-15T17:41:56","date_gmt":"2024-03-15T17:41:56","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-to-sort-a-hashmap-in-java\/"},"modified":"2024-03-21T14:15:33","modified_gmt":"2024-03-21T14:15:33","slug":"how-to-sort-a-hashmap-in-java","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-to-sort-a-hashmap-in-java\/","title":{"rendered":"How to sort a hashmap in Java?"},"content":{"rendered":"<p>In Java, HashMap is an unordered collection that does not store key-value pairs in a specific order. If you want to sort the elements in a HashMap, you can convert it to an ordered collection, such as TreeMap.<\/p>\n<p>TreeMap is an ordered map implemented based on red-black tree, which sorts the keys either according to their natural order or a custom Comparator. Here is an example of using a Comparator to sort a HashMap by keys.<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">import<\/span> java.util.*;\r\n\r\n<span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title class_\">SortHashMap<\/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        HashMap&lt;String, Integer&gt; hashMap = <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-title class_\">HashMap<\/span>&lt;&gt;();\r\n        hashMap.put(<span class=\"hljs-string\">\"Tom\"<\/span>, <span class=\"hljs-number\">30<\/span>);\r\n        hashMap.put(<span class=\"hljs-string\">\"Alice\"<\/span>, <span class=\"hljs-number\">25<\/span>);\r\n        hashMap.put(<span class=\"hljs-string\">\"Bob\"<\/span>, <span class=\"hljs-number\">35<\/span>);\r\n        hashMap.put(<span class=\"hljs-string\">\"John\"<\/span>, <span class=\"hljs-number\">40<\/span>);\r\n\r\n        TreeMap&lt;String, Integer&gt; sortedMap = <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-title class_\">TreeMap<\/span>&lt;&gt;(<span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-title class_\">Comparator<\/span>&lt;String&gt;() {\r\n            <span class=\"hljs-keyword\">public<\/span> <span class=\"hljs-type\">int<\/span> <span class=\"hljs-title function_\">compare<\/span><span class=\"hljs-params\">(String s1, String s2)<\/span> {\r\n                <span class=\"hljs-keyword\">return<\/span> s1.compareTo(s2); <span class=\"hljs-comment\">\/\/ \u6309\u7167\u952e\u7684\u81ea\u7136\u987a\u5e8f\u6392\u5e8f<\/span>\r\n            }\r\n        });\r\n        sortedMap.putAll(hashMap);\r\n\r\n        <span class=\"hljs-keyword\">for<\/span> (Map.Entry&lt;String, Integer&gt; entry : sortedMap.entrySet()) {\r\n            System.out.println(entry.getKey() + <span class=\"hljs-string\">\": \"<\/span> + entry.getValue());\r\n        }\r\n    }\r\n}\r\n<\/code><\/pre>\n<p>Output result:<\/p>\n<pre class=\"post-pre\"><code>Alice: 25\r\nBob: 35\r\nJohn: 40\r\nTom: 30\r\n<\/code><\/pre>\n<p>In this example, we start by creating a HashMap and adding some key-value pairs. Then, we create a TreeMap and provide a custom Comparator that compares the keys based on their natural order. Finally, we use the putAll() method to transfer the elements from the HashMap to the TreeMap, and use entrySet() to iterate through the sorted key-value pairs.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In Java, HashMap is an unordered collection that does not store key-value pairs in a specific order. If you want to sort the elements in a HashMap, you can convert it to an ordered collection, such as TreeMap. TreeMap is an ordered map implemented based on red-black tree, which sorts the keys either according to [&hellip;]<\/p>\n","protected":false},"author":13,"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-18835","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>How to sort a hashmap in Java? - 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\/how-to-sort-a-hashmap-in-java\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"How to sort a hashmap in Java?\" \/>\n<meta property=\"og:description\" content=\"In Java, HashMap is an unordered collection that does not store key-value pairs in a specific order. 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