{"id":3973,"date":"2018-06-09T21:56:31","date_gmt":"2018-06-09T13:56:31","guid":{"rendered":"https:\/\/ixyzero.com\/blog\/?p=3973"},"modified":"2018-06-09T21:56:31","modified_gmt":"2018-06-09T13:56:31","slug":"java%e4%b8%ad%e5%a6%82%e4%bd%95%e5%af%b9hashmap%e8%bf%9b%e8%a1%8c%e6%8e%92%e5%ba%8f","status":"publish","type":"post","link":"https:\/\/ixyzero.com\/blog\/archives\/3973.html","title":{"rendered":"Java\u4e2d\u5982\u4f55\u5bf9HashMap\u8fdb\u884c\u6392\u5e8f"},"content":{"rendered":"<p>=Start=<\/p>\n<h4 id=\"id-\u6a21\u677f-\u7f18\u7531\uff1a\">\u7f18\u7531\uff1a<\/h4>\n<p>Java\u4e2dHashMap\u7684\u503c\u662f\u6ca1\u6709\u987a\u5e8f\u7684\uff0c\u5b83\u662f\u6309\u7167key\u7684HashCode\u6765\u5b9e\u73b0\u7684\u3002\u5bf9\u4e8e\u8fd9\u4e2a\u65e0\u5e8f\u7684HashMap\u6211\u4eec\u8981\u600e\u4e48\u6765\u5b9e\u73b0\u6392\u5e8f\u5462\uff1f\u8fd9\u91cc\u5c31\u6574\u7406\u603b\u7ed3\u4e00\u4e0b\uff0c\u65b9\u4fbf\u4ee5\u540e\u67e5\u9605\u3001\u53c2\u8003\u3002<\/p>\n<h4 id=\"id-\u6a21\u677f-\u6b63\u6587\uff1a\">\u6b63\u6587\uff1a<\/h4>\n<h5 id=\"id-\u6a21\u677f-\u53c2\u8003\u89e3\u7b54\uff1a\">\u53c2\u8003\u89e3\u7b54\uff1a<\/h5>\n<p>\u5148\u8bf4\u7ed3\u8bba\uff0c\u5982\u679c\u7740\u6025\u7684\u8bdd\u53ef\u4ee5\u5148\u770b\u8fd9\u4e2a\/\u53ea\u770b\u8fd9\u4e2a\u5c31\u591f\uff1a<\/p>\n<p><span style=\"color: #000000;\"><strong>Java\u4e2d\u5bf9 HashMap \u8fdb\u884c\u6392\u5e8f\u7684\u4e00\u822c\u6b65\u9aa4\u5c31\u662f\uff1a<\/strong><\/span><\/p>\n<p><span style=\"color: #ff0000;\"><strong>1\u3001\u5148\u6839\u636e HashMap \u7684\u5185\u5bb9\u751f\u6210 list \uff1b<\/strong><\/span><br \/>\n<span style=\"color: #ff0000;\"><strong>2\u3001\u518d\u8c03\u7528 Collections.sort(list[, new Comparator]) \u5bf9 list \u8fdb\u884c\u5c31\u5730\u6392\u5e8f\uff1b<\/strong><\/span><br \/>\n2.1\u3001 \u5185\u90e8\u8fdb\u884c\u7684\u6bd4\u8f83\u4e00\u822c\u662f\u901a\u8fc7 .compareTo() \u65b9\u6cd5\u8fdb\u884c\u7684\uff0c\u4f46\u662f\u4e5f\u53ef\u4ee5\u81ea\u884c\u4fee\u6539\u300c\u5927\u4e8e\u8fd4\u56de1\uff0c\u5c0f\u4e8e\u8fd4\u56de-1\uff0c\u7b49\u4e8e\u8fd4\u56de0\u300d\uff1b<br \/>\n<span style=\"color: #ff0000;\"><strong>3\u3001 \u5982\u679c\u53ea\u8981\u6392\u5e8f\u540e\u7684\u7ed3\u679c\u7684\u8bdd\uff0c\u53ef\u4ee5\u76f4\u63a5\u7528 list \uff1b\u5982\u679c\u8fd8\u8981\u4e00\u4e2amap\u7684\u8bdd\uff0c\u5c31\u65b0\u5efa\u4e00\u4e2aLinkedHashMap\u6765\u5b58\u653elist\u7684\u7ed3\u679c\u3002<\/strong><\/span><\/p>\n<hr \/>\n<p><span style=\"color: #000000;\"><strong>Java\u4e2d\u7684\u539f\u751f\u6392\u5e8f\u65b9\u6cd5\u6574\u7406\uff1a<\/strong><\/span><\/p>\n<ul>\n<li>\u5bf9\u57fa\u672c\u7c7b\u578b\u6392\u5e8f # Arrays.sort()<\/li>\n<li>\u5bf9\u5bf9\u8c61\u6570\u7ec4\u6392\u5e8f # \u5219\u8981\u81ea\u5df1\u5b9e\u73b0 java.util.Comparator \u63a5\u53e3<\/li>\n<\/ul>\n<pre class=\"lang:default decode:true \">\/\/1. \u6570\u5b57\u6392\u5e8f\r\nint[] intArray = new int[] { 4, 1, 3, -23 };\r\nArrays.sort(intArray);\r\nSystem.out.println(Arrays.toString(intArray));\r\n\/\/\u8f93\u51fa\uff1a [-23, 1, 3, 4]\r\n\r\n\/\/2. \u5b57\u7b26\u4e32\u6392\u5e8f\uff0c\u5148\u5927\u5199\u540e\u5c0f\u5199\r\nString[] strArray = new String[] { \"z\", \"a\", \"C\" };\r\nSystem.out.println(Arrays.toString(strArray));\r\n\/\/\u8f93\u51fa\uff1a [z, a, C]\r\nArrays.sort(strArray);\r\nSystem.out.println(Arrays.toString(strArray));\r\n\/\/\u8f93\u51fa\uff1a [C, a, z]\r\n\r\n\/\/3. \u4e25\u683c\u6309\u5b57\u6bcd\u8868\u987a\u5e8f\u6392\u5e8f\uff0c\u4e5f\u5c31\u662f\u5ffd\u7565\u5927\u5c0f\u5199\u6392\u5e8f Case-insensitive sort\r\nArrays.sort(strArray, String.CASE_INSENSITIVE_ORDER);\r\nSystem.out.println(Arrays.toString(strArray));\r\n\/\/\u8f93\u51fa\uff1a [a, C, z]\r\n\r\n\/\/4. \u53cd\u5411\u6392\u5e8f\uff0c Reverse-order sort\r\nArrays.sort(strArray, Collections.reverseOrder());\r\nSystem.out.println(Arrays.toString(strArray));\r\n\/\/\u8f93\u51fa\uff1a [z, a, C]\r\n\r\n\/\/5. \u5ffd\u7565\u5927\u5c0f\u5199\u53cd\u5411\u6392\u5e8f Case-insensitive reverse-order sort\r\nArrays.sort(strArray, String.CASE_INSENSITIVE_ORDER);\r\nCollections.reverse(Arrays.asList(strArray));\r\nSystem.out.println(Arrays.toString(strArray));\r\n\/\/\u8f93\u51fa\uff1a [z, C, a]<\/pre>\n<p>Java\u4e2d\u6253\u5370\u6570\u7ec4\u7684\u65b9\u6cd5\uff0c\u53c2\u8003\u300c<a href=\"https:\/\/stackoverflow.com\/questions\/409784\/whats-the-simplest-way-to-print-a-java-array\">\u94fe\u63a5<\/a>\u300d\u3002<\/p>\n<hr \/>\n<p>\u518d\u653e\u6574\u7406\u540e\u7684\u4ee3\u7801\uff1a<\/p>\n<pre class=\"lang:default decode:true \">package com.ixyzero.learn.misc;\r\n\r\nimport java.util.*;\r\nimport java.util.Map.Entry;\r\n\r\n\/**\r\n * https:\/\/stackoverflow.com\/questions\/8119366\/sorting-hashmap-by-values\/13913206#13913206\r\n *\/\r\npublic class SortMapByValue\r\n{\r\n    public static boolean ASC = true;\r\n    public static boolean DESC = false;\r\n\r\n    public static void main(String[] args)\r\n    {\r\n        \/\/ Creating dummy unsorted map\r\n        Map&lt;String, Integer&gt; unsortedMap = new HashMap&lt;&gt;();\r\n        unsortedMap.put(\"B\", 55);\r\n        unsortedMap.put(\"A\", 80);\r\n        unsortedMap.put(\"D\", 20);\r\n        unsortedMap.put(\"C\", 70);\r\n\r\n        System.out.println(\"Before sorting......\");\r\n        printMap(unsortedMap);\r\n\r\n        System.out.println(\"\\nAfter sorting ascending order......\");\r\n        Map&lt;String, Integer&gt; sortedMapAsc = sortByValueComparator(unsortedMap, ASC);\r\n        printMap(sortedMapAsc);\r\n\r\n        System.out.println(\"\\nAfter sorting descending order......\");\r\n        Map&lt;String, Integer&gt; sortedMapDesc = sortByValueComparator(unsortedMap, DESC);\r\n        printMap(sortedMapDesc);\r\n\r\n        System.out.println(\"\\nAfter sorting descending order by key......\");\r\n        Map&lt;String, Integer&gt; sortedKeyMapDesc = sortByKeyComparator(sortedMapAsc, DESC);\r\n        printMap(sortedKeyMapDesc);\r\n    }\r\n\r\n    private static Map&lt;String, Integer&gt; sortByKeyComparator(Map&lt;String, Integer&gt; unsortedMap, final boolean order)\r\n    {\r\n\r\n        List&lt;Map.Entry&lt;String, Integer&gt;&gt; list = new LinkedList&lt;&gt;(unsortedMap.entrySet());\r\n\r\n        \/\/ Sorting the list based on values\r\n        Collections.sort(list, new Comparator&lt;Map.Entry&lt;String, Integer&gt;&gt;() {\r\n            public int compare(Map.Entry&lt;String, Integer&gt; o1, Map.Entry&lt;String, Integer&gt; o2) {\r\n                if (order) {\r\n                    return o1.getKey().toString().compareTo(o2.getKey().toString());\r\n                } else {\r\n                    return o2.getKey().toString().compareTo(o1.getKey().toString());\r\n                }\r\n            }\r\n        });\r\n\r\n        \/\/ Maintaining insertion order with the help of LinkedList\r\n        Map&lt;String, Integer&gt; sortedMap = new LinkedHashMap&lt;&gt;();\r\n        for (Map.Entry&lt;String, Integer&gt; entry : list) {\r\n            sortedMap.put(entry.getKey(), entry.getValue());\r\n        }\r\n\r\n        return sortedMap;\r\n    }\r\n\r\n\r\n    private static Map&lt;String, Integer&gt; sortByValueComparator(Map&lt;String, Integer&gt; unsortedMap, final boolean order)\r\n    {\r\n\r\n        List&lt;Map.Entry&lt;String, Integer&gt;&gt; list = new LinkedList&lt;&gt;(unsortedMap.entrySet());\r\n\r\n        \/\/ Sorting the list based on values\r\n        Collections.sort(list, new Comparator&lt;Map.Entry&lt;String, Integer&gt;&gt;() {\r\n            public int compare(Map.Entry&lt;String, Integer&gt; o1, Map.Entry&lt;String, Integer&gt; o2) {\r\n                if (order) {\r\n                    return o1.getValue().compareTo(o2.getValue());\r\n                } else {\r\n                    return o2.getValue().compareTo(o1.getValue());\r\n                }\r\n            }\r\n        });\r\n\r\n        \/\/ Maintaining insertion order with the help of LinkedList\r\n        Map&lt;String, Integer&gt; sortedMap = new LinkedHashMap&lt;&gt;();\r\n        for (Map.Entry&lt;String, Integer&gt; entry : list) {\r\n            sortedMap.put(entry.getKey(), entry.getValue());\r\n        }\r\n\r\n        return sortedMap;\r\n    }\r\n\r\n    public static void printMap(Map&lt;String, Integer&gt; map)\r\n    {\r\n        for (Entry&lt;String, Integer&gt; entry : map.entrySet()) {\r\n            System.out.println(\"Key: \" + entry.getKey() + \"\\tValue: \"+ entry.getValue());\r\n        }\r\n    }\r\n}<\/pre>\n<p>&nbsp;<\/p>\n<h5 id=\"id-\u6a21\u677f-\u53c2\u8003\u94fe\u63a5\uff1a\">\u53c2\u8003\u94fe\u63a5\uff1a<\/h5>\n<ul>\n<li><a href=\"https:\/\/stackoverflow.com\/questions\/780541\/how-to-sort-a-hashmap-in-java\/16745398#16745398\">Java\u4e2d\u5bf9HashMap\u8fdb\u884c\u6392\u5e8f<\/a><\/li>\n<li><a href=\"https:\/\/stackoverflow.com\/questions\/109383\/sort-a-mapkey-value-by-values\">https:\/\/stackoverflow.com\/questions\/109383\/sort-a-mapkey-value-by-values<\/a><\/li>\n<li><a href=\"https:\/\/stackoverflow.com\/questions\/8119366\/sorting-hashmap-by-values\/13913206#13913206\">https:\/\/stackoverflow.com\/questions\/8119366\/sorting-hashmap-by-values\/13913206#13913206<\/a><\/li>\n<li><a href=\"https:\/\/blog.csdn.net\/basycia\/article\/details\/51886837\">Java\u539f\u751f\u6392\u5e8f\u65b9\u6cd5\u603b\u7ed3&#8211;HashMap\u6392\u5e8f<\/a><\/li>\n<li><a href=\"https:\/\/blog.csdn.net\/u012730840\/article\/details\/19703101\">java\u5bf9HashMap\u4e2d\u7684key\u6216\u8005value\u503c\u8fdb\u884c\u6392\u5e8f\uff01<\/a><\/li>\n<li><a href=\"https:\/\/www.cnblogs.com\/lovebread\/archive\/2009\/11\/23\/1609121.html\">[Java]HashMap\u7684\u4e24\u79cd\u6392\u5e8f\u65b9\u5f0f<\/a><\/li>\n<li><a href=\"https:\/\/blog.csdn.net\/xifeijian\/article\/details\/46522531\">https:\/\/blog.csdn.net\/xifeijian\/article\/details\/46522531<\/a><\/li>\n<li><a href=\"https:\/\/blog.csdn.net\/zxy_snow\/article\/details\/6979263\">Java\u4e2dHashmap\u6309key\u6392\u5e8f<\/a><\/li>\n<li><a href=\"https:\/\/blog.csdn.net\/buptdavid\/article\/details\/4807835\">HashMap\u904d\u5386\u4e0e\u6309key\u6392\u5e8f\u3002<\/a><\/li>\n<\/ul>\n<p>=END=<\/p>\n","protected":false},"excerpt":{"rendered":"<p>=Start= \u7f18\u7531\uff1a Java\u4e2dHashMap\u7684\u503c\u662f\u6ca1\u6709\u987a\u5e8f\u7684\uff0c\u5b83\u662f\u6309\u7167key\u7684HashCode\u6765\u5b9e\u73b0\u7684\u3002\u5bf9 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23,7],"tags":[1152,1151,61,342,292],"class_list":["post-3973","post","type-post","status-publish","format-standard","hentry","category-knowledgebase-2","category-programing","tag-compareto","tag-hashmap","tag-java","tag-map","tag-sort"],"views":13022,"_links":{"self":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/3973","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/comments?post=3973"}],"version-history":[{"count":1,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/3973\/revisions"}],"predecessor-version":[{"id":3974,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/posts\/3973\/revisions\/3974"}],"wp:attachment":[{"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/media?parent=3973"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/categories?post=3973"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ixyzero.com\/blog\/wp-json\/wp\/v2\/tags?post=3973"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}