{"id":137,"date":"2025-07-12T20:04:53","date_gmt":"2025-07-12T12:04:53","guid":{"rendered":"https:\/\/yingjun.run\/?p=137"},"modified":"2025-07-13T15:16:11","modified_gmt":"2025-07-13T07:16:11","slug":"java%e9%9b%86%e5%90%88%e4%b8%8a","status":"publish","type":"post","link":"https:\/\/yingjun.run\/index.php\/2025\/07\/12\/java%e9%9b%86%e5%90%88%e4%b8%8a\/","title":{"rendered":"Java\u96c6\u5408"},"content":{"rendered":"<h3><span class=\"ez-toc-section\" id=\"Java_%E9%9B%86%E5%90%88%E6%A6%82%E8%A7%88\"><\/span>Java \u96c6\u5408\u6982\u89c8<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Java \u96c6\u5408\uff0c\u4e5f\u53eb\u4f5c\u5bb9\u5668\uff0c\u4e3b\u8981\u662f\u7531\u4e24\u5927\u63a5\u53e3\u6d3e\u751f\u800c\u6765\uff1a\u4e00\u4e2a\u662f Collection\u63a5\u53e3\uff0c\u4e3b\u8981\u7528\u4e8e\u5b58\u653e\u5355\u4e00\u5143\u7d20\uff1b\u53e6\u4e00\u4e2a\u662f Map \u63a5\u53e3\uff0c\u4e3b\u8981\u7528\u4e8e\u5b58\u653e\u952e\u503c\u5bf9\u3002\u5bf9\u4e8eCollection \u63a5\u53e3\uff0c\u4e0b\u9762\u53c8\u6709\u4e09\u4e2a\u4e3b\u8981\u7684\u5b50\u63a5\u53e3\uff1aList\u3001Set \u3001 Queue\u3002<br \/>\n<img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752319919145.png\" alt=\"file\" \/><\/p>\n<h3><span class=\"ez-toc-section\" id=\"%E8%AF%B4%E8%AF%B4_List_Set_Queue_Map_%E5%9B%9B%E8%80%85%E7%9A%84%E5%8C%BA%E5%88%AB%EF%BC%9F\"><\/span>\u8bf4\u8bf4 List, Set, Queue, Map \u56db\u8005\u7684\u533a\u522b\uff1f<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>List(\u5bf9\u4ed8\u987a\u5e8f\u7684\u597d\u5e2e\u624b): \u5b58\u50a8\u7684\u5143\u7d20\u662f\u6709\u5e8f\u7684\u3001\u53ef\u91cd\u590d\u7684\u3002<br \/>\nSet(\u6ce8\u91cd\u72ec\u4e00\u65e0\u4e8c\u7684\u6027\u8d28): \u5b58\u50a8\u7684\u5143\u7d20\u4e0d\u53ef\u91cd\u590d\u7684\u3002<br \/>\nQueue(\u5b9e\u73b0\u6392\u961f\u529f\u80fd\u7684\u53eb\u53f7\u673a): \u6309\u7279\u5b9a\u7684\u6392\u961f\u89c4\u5219\u6765\u786e\u5b9a\u5148\u540e\u987a\u5e8f\uff0c\u5b58\u50a8\u7684\u5143\u7d20\u662f\u6709\u5e8f\u7684\u3001\u53ef\u91cd\u590d\u7684\u3002<br \/>\nMap(\u7528 key \u6765\u641c\u7d22\u7684\u4e13\u5bb6): \u4f7f\u7528\u952e\u503c\u5bf9\uff08key-value\uff09\u5b58\u50a8\uff0c\u7c7b\u4f3c\u4e8e\u6570\u5b66\u4e0a\u7684\u51fd\u6570 y=f(x)\uff0c&quot;x&quot; \u4ee3\u8868 key\uff0c&quot;y&quot; \u4ee3\u8868 value\uff0ckey \u662f\u65e0\u5e8f\u7684\u3001\u4e0d\u53ef\u91cd\u590d\u7684\uff0cvalue \u662f\u65e0\u5e8f\u7684\u3001\u53ef\u91cd\u590d\u7684\uff0c\u6bcf\u4e2a\u952e\u6700\u591a\u6620\u5c04\u5230\u4e00\u4e2a\u503c<\/p>\n<h3><span class=\"ez-toc-section\" id=\"ArrayList_%E5%92%8C_Array%EF%BC%88%E6%95%B0%E7%BB%84%EF%BC%89%E7%9A%84%E5%8C%BA%E5%88%AB%EF%BC%9F\"><\/span>ArrayList \u548c Array\uff08\u6570\u7ec4\uff09\u7684\u533a\u522b\uff1f<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>ArrayList \u5185\u90e8\u57fa\u4e8e\u52a8\u6001\u6570\u7ec4\u5b9e\u73b0\uff0c\u6bd4 Array\uff08\u9759\u6001\u6570\u7ec4\uff09 \u4f7f\u7528\u8d77\u6765\u66f4\u52a0\u7075\u6d3b\uff1a<br \/>\nArrayList\u4f1a\u6839\u636e\u5b9e\u9645\u5b58\u50a8\u7684\u5143\u7d20\u52a8\u6001\u5730\u6269\u5bb9\u6216\u7f29\u5bb9\uff0c\u800c Array \u88ab\u521b\u5efa\u4e4b\u540e\u5c31\u4e0d\u80fd\u6539\u53d8\u5b83\u7684\u957f\u5ea6\u4e86\u3002<br \/>\nArrayList \u5141\u8bb8\u4f60\u4f7f\u7528\u6cdb\u578b\u6765\u786e\u4fdd\u7c7b\u578b\u5b89\u5168\uff0cArray \u5219\u4e0d\u53ef\u4ee5\u3002<br \/>\nArrayList \u4e2d\u53ea\u80fd\u5b58\u50a8\u5bf9\u8c61\u3002\u5bf9\u4e8e\u57fa\u672c\u7c7b\u578b\u6570\u636e\uff0c\u9700\u8981\u4f7f\u7528\u5176\u5bf9\u5e94\u7684\u5305\u88c5\u7c7b\uff08\u5982 Integer\u3001Double \u7b49\uff09\u3002Array \u53ef\u4ee5\u76f4\u63a5\u5b58\u50a8\u57fa\u672c\u7c7b\u578b\u6570\u636e\uff0c\u4e5f\u53ef\u4ee5\u5b58\u50a8\u5bf9\u8c61\u3002<br \/>\nArrayList \u652f\u6301\u63d2\u5165\u3001\u5220\u9664\u3001\u904d\u5386\u7b49\u5e38\u89c1\u64cd\u4f5c\uff0c\u5e76\u4e14\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684 API \u64cd\u4f5c\u65b9\u6cd5\uff0c\u6bd4\u5982 add()\u3001remove()\u7b49\u3002Array \u53ea\u662f\u4e00\u4e2a\u56fa\u5b9a\u957f\u5ea6\u7684\u6570\u7ec4\uff0c\u53ea\u80fd\u6309\u7167\u4e0b\u6807\u8bbf\u95ee\u5176\u4e2d\u7684\u5143\u7d20\uff0c\u4e0d\u5177\u5907\u52a8\u6001\u6dfb\u52a0\u3001\u5220\u9664\u5143\u7d20\u7684\u80fd\u529b\u3002<br \/>\nArrayList\u521b\u5efa\u65f6\u4e0d\u9700\u8981\u6307\u5b9a\u5927\u5c0f\uff0c\u800cArray\u521b\u5efa\u65f6\u5fc5\u987b\u6307\u5b9a\u5927\u5c0f\u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"ArrayList_%E5%92%8C_Vector_%E7%9A%84%E5%8C%BA%E5%88%AB\"><\/span>ArrayList \u548c Vector \u7684\u533a\u522b?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>ArrayList \u662f List \u7684\u4e3b\u8981\u5b9e\u73b0\u7c7b\uff0c\u5e95\u5c42\u4f7f\u7528 Object[]\u5b58\u50a8\uff0c\u9002\u7528\u4e8e\u9891\u7e41\u7684\u67e5\u627e\u5de5\u4f5c\uff0c\u7ebf\u7a0b\u4e0d\u5b89\u5168 \u3002Vector \u662f List \u7684\u53e4\u8001\u5b9e\u73b0\u7c7b\uff0c\u5e95\u5c42\u4f7f\u7528Object[] \u5b58\u50a8\uff0c\u7ebf\u7a0b\u5b89\u5168\u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Vector_%E5%92%8C_Stack_%E7%9A%84%E5%8C%BA%E5%88%AB\"><\/span>Vector \u548c Stack \u7684\u533a\u522b?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Vector \u548c Stack \u4e24\u8005\u90fd\u662f\u7ebf\u7a0b\u5b89\u5168\u7684\uff0c\u90fd\u662f\u4f7f\u7528 synchronized \u5173\u952e\u5b57\u8fdb\u884c\u540c\u6b65\u5904\u7406\u3002<br \/>\nStack \u7ee7\u627f\u81ea Vector\uff0c\u662f\u4e00\u4e2a\u540e\u8fdb\u5148\u51fa\u7684\u6808\uff0c\u800c Vector \u662f\u4e00\u4e2a\u5217\u8868\u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"LinkedList_%E4%B8%BA%E4%BB%80%E4%B9%88%E4%B8%8D%E8%83%BD%E5%AE%9E%E7%8E%B0_RandomAccess_%E6%8E%A5%E5%8F%A3%EF%BC%9F\"><\/span>LinkedList \u4e3a\u4ec0\u4e48\u4e0d\u80fd\u5b9e\u73b0 RandomAccess \u63a5\u53e3\uff1f<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>RandomAccess \u662f\u4e00\u4e2a\u6807\u8bb0\u63a5\u53e3\uff0c\u7528\u6765\u8868\u660e\u5b9e\u73b0\u8be5\u63a5\u53e3\u7684\u7c7b\u652f\u6301\u968f\u673a\u8bbf\u95ee\uff08\u5373\u53ef\u4ee5\u901a\u8fc7\u7d22\u5f15\u5feb\u901f\u8bbf\u95ee\u5143\u7d20\uff09\u3002\u7531\u4e8e LinkedList \u5e95\u5c42\u6570\u636e\u7ed3\u6784\u662f\u94fe\u8868\uff0c\u5185\u5b58\u5730\u5740\u4e0d\u8fde\u7eed\uff0c\u53ea\u80fd\u901a\u8fc7\u6307\u9488\u6765\u5b9a\u4f4d\uff0c\u4e0d\u652f\u6301\u968f\u673a\u5feb\u901f\u8bbf\u95ee\uff0c\u6240\u4ee5\u4e0d\u80fd\u5b9e\u73b0 RandomAccess \u63a5\u53e3\u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"ArrayList_%E4%B8%8E_LinkedList_%E5%8C%BA%E5%88%AB\"><\/span>ArrayList \u4e0e LinkedList \u533a\u522b?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><strong>\u662f\u5426\u4fdd\u8bc1\u7ebf\u7a0b\u5b89\u5168<\/strong>\uff1a ArrayList \u548c LinkedList \u90fd\u662f\u4e0d\u540c\u6b65\u7684\uff0c\u4e5f\u5c31\u662f\u4e0d\u4fdd\u8bc1\u7ebf\u7a0b\u5b89\u5168\uff1b<br \/>\n<strong>\u5e95\u5c42\u6570\u636e\u7ed3\u6784<\/strong>\uff1a ArrayList \u5e95\u5c42\u4f7f\u7528\u7684\u662f Object \u6570\u7ec4\uff1bLinkedList \u5e95\u5c42\u4f7f\u7528\u7684\u662f \u53cc\u5411\u94fe\u8868 \u6570\u636e\u7ed3\u6784\uff08JDK1.6 \u4e4b\u524d\u4e3a\u5faa\u73af\u94fe\u8868\uff0cJDK1.7 \u53d6\u6d88\u4e86\u5faa\u73af\u3002\u6ce8\u610f\u53cc\u5411\u94fe\u8868\u548c\u53cc\u5411\u5faa\u73af\u94fe\u8868\u7684\u533a\u522b\uff0c\u4e0b\u9762\u6709\u4ecb\u7ecd\u5230\uff01\uff09<br \/>\n<strong>\u63d2\u5165\u548c\u5220\u9664\u662f\u5426\u53d7\u5143\u7d20\u4f4d\u7f6e\u7684\u5f71\u54cd<\/strong>\uff1aArrayList \u91c7\u7528\u6570\u7ec4\u5b58\u50a8\uff0c\u6240\u4ee5\u63d2\u5165\u548c\u5220\u9664\u5143\u7d20\u7684\u65f6\u95f4\u590d\u6742\u5ea6\u53d7\u5143\u7d20\u4f4d\u7f6e\u7684\u5f71\u54cd\u3002 \u6bd4\u5982\uff1a\u6267\u884cadd(E e)\u65b9\u6cd5\u7684\u65f6\u5019\uff0c ArrayList \u4f1a\u9ed8\u8ba4\u5728\u5c06\u6307\u5b9a\u7684\u5143\u7d20\u8ffd\u52a0\u5230\u6b64\u5217\u8868\u7684\u672b\u5c3e\uff0c\u8fd9\u79cd\u60c5\u51b5\u65f6\u95f4\u590d\u6742\u5ea6\u5c31\u662f O(1)\u3002\u4f46\u662f\u5982\u679c\u8981\u5728\u6307\u5b9a\u4f4d\u7f6e i \u63d2\u5165\u548c\u5220\u9664\u5143\u7d20\u7684\u8bdd\uff08add(int index, E element)\uff09\uff0c\u65f6\u95f4\u590d\u6742\u5ea6\u5c31\u4e3a O(n)\u3002\u56e0\u4e3a\u5728\u8fdb\u884c\u4e0a\u8ff0\u64cd\u4f5c\u7684\u65f6\u5019\u96c6\u5408\u4e2d\u7b2c i \u548c\u7b2c i \u4e2a\u5143\u7d20\u4e4b\u540e\u7684(n-i)\u4e2a\u5143\u7d20\u90fd\u8981\u6267\u884c\u5411\u540e\u4f4d\/\u5411\u524d\u79fb\u4e00\u4f4d\u7684\u64cd\u4f5c\u3002LinkedList \u91c7\u7528\u94fe\u8868\u5b58\u50a8\uff0c\u6240\u4ee5\u5728\u5934\u5c3e\u63d2\u5165\u6216\u8005\u5220\u9664\u5143\u7d20\u4e0d\u53d7\u5143\u7d20\u4f4d\u7f6e\u7684\u5f71\u54cd\uff08add(E e)\u3001addFirst(E e)\u3001addLast(E e)\u3001removeFirst()\u3001 removeLast()\uff09\uff0c\u65f6\u95f4\u590d\u6742\u5ea6\u4e3a O(1)\uff0c\u5982\u679c\u662f\u8981\u5728\u6307\u5b9a\u4f4d\u7f6e i \u63d2\u5165\u548c\u5220\u9664\u5143\u7d20\u7684\u8bdd\uff08add(int index, E element)\uff0cremove(Object o),remove(int index)\uff09\uff0c \u65f6\u95f4\u590d\u6742\u5ea6\u4e3a O(n) \uff0c\u56e0\u4e3a\u9700\u8981\u5148\u79fb\u52a8\u5230\u6307\u5b9a\u4f4d\u7f6e\u518d\u63d2\u5165\u548c\u5220\u9664\u3002<br \/>\n<strong>\u662f\u5426\u652f\u6301\u5feb\u901f\u968f\u673a\u8bbf\u95ee\uff1a<\/strong>LinkedList \u4e0d\u652f\u6301\u9ad8\u6548\u7684\u968f\u673a\u5143\u7d20\u8bbf\u95ee\uff0c\u800c ArrayList\uff08\u5b9e\u73b0\u4e86 RandomAccess \u63a5\u53e3\uff09 \u652f\u6301\u3002\u5feb\u901f\u968f\u673a\u8bbf\u95ee\u5c31\u662f\u901a\u8fc7\u5143\u7d20\u7684\u5e8f\u53f7\u5feb\u901f\u83b7\u53d6\u5143\u7d20\u5bf9\u8c61(\u5bf9\u5e94\u4e8eget(int index)\u65b9\u6cd5)\u3002<br \/>\n<strong>\u5185\u5b58\u7a7a\u95f4\u5360\u7528\uff1a<\/strong> ArrayList \u7684\u7a7a\u95f4\u6d6a\u8d39\u4e3b\u8981\u4f53\u73b0\u5728\u5728 list \u5217\u8868\u7684\u7ed3\u5c3e\u4f1a\u9884\u7559\u4e00\u5b9a\u7684\u5bb9\u91cf\u7a7a\u95f4\uff0c\u800c LinkedList \u7684\u7a7a\u95f4\u82b1\u8d39\u5219\u4f53\u73b0\u5728\u5b83\u7684\u6bcf\u4e00\u4e2a\u5143\u7d20\u90fd\u9700\u8981\u6d88\u8017\u6bd4 ArrayList \u66f4\u591a\u7684\u7a7a\u95f4\uff08\u56e0\u4e3a\u8981\u5b58\u653e\u76f4\u63a5\u540e\u7ee7\u548c\u76f4\u63a5\u524d\u9a71\u4ee5\u53ca\u6570\u636e\uff09\u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"%E8%AF%B4%E4%B8%80%E8%AF%B4_ArrayList_%E7%9A%84%E6%89%A9%E5%AE%B9%E6%9C%BA%E5%88%B6%E5%90%A7\"><\/span>\u8bf4\u4e00\u8bf4 ArrayList \u7684\u6269\u5bb9\u673a\u5236\u5427<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><a href=\"https:\/\/javaguide.cn\/java\/collection\/arraylist-source-code.html#%E5%85%88%E4%BB%8E-arraylist-%E7%9A%84%E6%9E%84%E9%80%A0%E5%87%BD%E6%95%B0%E8%AF%B4%E8%B5%B7\" title=\"ArrayList \u6269\u5bb9\u673a\u5236\">ArrayList \u6269\u5bb9\u673a\u5236<\/a><\/p>\n<h3><span class=\"ez-toc-section\" id=\"Comparable_%E5%92%8C_Comparator_%E7%9A%84%E5%8C%BA%E5%88%AB\"><\/span>Comparable \u548c Comparator \u7684\u533a\u522b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Comparable \u63a5\u53e3\u548c Comparator \u63a5\u53e3\u90fd\u662f Java \u4e2d\u7528\u4e8e\u6392\u5e8f\u7684\u63a5\u53e3\uff0c\u5b83\u4eec\u5728\u5b9e\u73b0\u7c7b\u5bf9\u8c61\u4e4b\u95f4\u6bd4\u8f83\u5927\u5c0f\u3001\u6392\u5e8f\u7b49\u65b9\u9762\u53d1\u6325\u4e86\u91cd\u8981\u4f5c\u7528\uff1aComparable \u63a5\u53e3\u5b9e\u9645\u4e0a\u662f\u51fa\u81eajava.lang\u5305 \u5b83\u6709\u4e00\u4e2a compareTo(Object obj)\u65b9\u6cd5\u7528\u6765\u6392\u5e8fComparator\u63a5\u53e3\u5b9e\u9645\u4e0a\u662f\u51fa\u81ea java.util \u5305\u5b83\u6709\u4e00\u4e2acompare(Object obj1, Object obj2)\u65b9\u6cd5\u7528\u6765\u6392\u5e8f<\/p>\n<h3><span class=\"ez-toc-section\" id=\"%E6%97%A0%E5%BA%8F%E6%80%A7%E5%92%8C%E4%B8%8D%E5%8F%AF%E9%87%8D%E5%A4%8D%E6%80%A7%E7%9A%84%E5%90%AB%E4%B9%89%E6%98%AF%E4%BB%80%E4%B9%88\"><\/span>\u65e0\u5e8f\u6027\u548c\u4e0d\u53ef\u91cd\u590d\u6027\u7684\u542b\u4e49\u662f\u4ec0\u4e48<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>\u65e0\u5e8f\u6027\u4e0d\u7b49\u4e8e\u968f\u673a\u6027 \uff0c\u65e0\u5e8f\u6027\u662f\u6307\u5b58\u50a8\u7684\u6570\u636e\u5728\u5e95\u5c42\u6570\u7ec4\u4e2d\u5e76\u975e\u6309\u7167\u6570\u7ec4\u7d22\u5f15\u7684\u987a\u5e8f\u6dfb\u52a0 \uff0c\u800c\u662f\u6839\u636e\u6570\u636e\u7684\u54c8\u5e0c\u503c\u51b3\u5b9a\u7684\u3002<br \/>\n\u4e0d\u53ef\u91cd\u590d\u6027\u662f\u6307\u6dfb\u52a0\u7684\u5143\u7d20\u6309\u7167 equals() \u5224\u65ad\u65f6 \uff0c\u8fd4\u56de false\uff0c\u9700\u8981\u540c\u65f6\u91cd\u5199 equals() \u65b9\u6cd5\u548c hashCode() \u65b9\u6cd5\u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"%E6%AF%94%E8%BE%83_HashSet%E3%80%81LinkedHashSet_%E5%92%8C_TreeSet_%E4%B8%89%E8%80%85%E7%9A%84%E5%BC%82%E5%90%8C\"><\/span>\u6bd4\u8f83 HashSet\u3001LinkedHashSet \u548c TreeSet \u4e09\u8005\u7684\u5f02\u540c<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>HashSet\u3001LinkedHashSet \u548c TreeSet \u90fd\u662f Set \u63a5\u53e3\u7684\u5b9e\u73b0\u7c7b\uff0c\u90fd\u80fd\u4fdd\u8bc1\u5143\u7d20\u552f\u4e00\uff0c\u5e76\u4e14\u90fd\u4e0d\u662f\u7ebf\u7a0b\u5b89\u5168\u7684\u3002<br \/>\nHashSet\u3001LinkedHashSet \u548c TreeSet \u7684\u4e3b\u8981\u533a\u522b\u5728\u4e8e\u5e95\u5c42\u6570\u636e\u7ed3\u6784\u4e0d\u540c\u3002HashSet \u7684\u5e95\u5c42\u6570\u636e\u7ed3\u6784\u662f\u54c8\u5e0c\u8868\uff08\u57fa\u4e8e HashMap \u5b9e\u73b0\uff09\u3002LinkedHashSet \u7684\u5e95\u5c42\u6570\u636e\u7ed3\u6784\u662f\u94fe\u8868\u548c\u54c8\u5e0c\u8868\uff0c\u5143\u7d20\u7684\u63d2\u5165\u548c\u53d6\u51fa\u987a\u5e8f\u6ee1\u8db3 FIFO\u3002TreeSet \u5e95\u5c42\u6570\u636e\u7ed3\u6784\u662f\u7ea2\u9ed1\u6811\uff0c\u5143\u7d20\u662f\u6709\u5e8f\u7684\uff0c\u6392\u5e8f\u7684\u65b9\u5f0f\u6709\u81ea\u7136\u6392\u5e8f\u548c\u5b9a\u5236\u6392\u5e8f\u3002\u5e95\u5c42\u6570\u636e\u7ed3\u6784\u4e0d\u540c\u53c8\u5bfc\u81f4\u8fd9\u4e09\u8005\u7684\u5e94\u7528\u573a\u666f\u4e0d\u540c\u3002HashSet \u7528\u4e8e\u4e0d\u9700\u8981\u4fdd\u8bc1\u5143\u7d20\u63d2\u5165\u548c\u53d6\u51fa\u987a\u5e8f\u7684\u573a\u666f\uff0cLinkedHashSet \u7528\u4e8e\u4fdd\u8bc1\u5143\u7d20\u7684\u63d2\u5165\u548c\u53d6\u51fa\u987a\u5e8f\u6ee1\u8db3 FIFO \u7684\u573a\u666f\uff0cTreeSet \u7528\u4e8e\u652f\u6301\u5bf9\u5143\u7d20\u81ea\u5b9a\u4e49\u6392\u5e8f\u89c4\u5219\u7684\u573a\u666f\u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Queue_%E4%B8%8E_Deque_%E7%9A%84%E5%8C%BA%E5%88%AB\"><\/span>Queue \u4e0e Deque \u7684\u533a\u522b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Queue \u662f\u5355\u7aef\u961f\u5217\uff0c\u53ea\u80fd\u4ece\u4e00\u7aef\u63d2\u5165\u5143\u7d20\uff0c\u53e6\u4e00\u7aef\u5220\u9664\u5143\u7d20\uff0c\u5b9e\u73b0\u4e0a\u4e00\u822c\u9075\u5faa \u5148\u8fdb\u5148\u51fa\uff08FIFO\uff09 \u89c4\u5219\u3002Queue \u6269\u5c55\u4e86 Collection \u7684\u63a5\u53e3\uff0c\u6839\u636e \u56e0\u4e3a\u5bb9\u91cf\u95ee\u9898\u800c\u5bfc\u81f4\u64cd\u4f5c\u5931\u8d25\u540e\u5904\u7406\u65b9\u5f0f\u7684\u4e0d\u540c \u53ef\u4ee5\u5206\u4e3a\u4e24\u7c7b\u65b9\u6cd5: \u4e00\u79cd\u5728\u64cd\u4f5c\u5931\u8d25\u540e\u4f1a\u629b\u51fa\u5f02\u5e38\uff0c\u53e6\u4e00\u79cd\u5219\u4f1a\u8fd4\u56de\u7279\u6b8a\u503c\u3002<br \/>\n<img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752320889612.png\" alt=\"file\" \/><br \/>\nDeque \u662f\u53cc\u7aef\u961f\u5217\uff0c\u5728\u961f\u5217\u7684\u4e24\u7aef\u5747\u53ef\u4ee5\u63d2\u5165\u6216\u5220\u9664\u5143\u7d20\u3002<br \/>\nDeque \u6269\u5c55\u4e86 Queue \u7684\u63a5\u53e3, \u589e\u52a0\u4e86\u5728\u961f\u9996\u548c\u961f\u5c3e\u8fdb\u884c\u63d2\u5165\u548c\u5220\u9664\u7684\u65b9\u6cd5\uff0c\u540c\u6837\u6839\u636e\u5931\u8d25\u540e\u5904\u7406\u65b9\u5f0f\u7684\u4e0d\u540c\u5206\u4e3a\u4e24\u7c7b\uff1a<br \/>\n<img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752320903787.png\" alt=\"file\" \/><\/p>\n<h3><span class=\"ez-toc-section\" id=\"ArrayDeque_%E4%B8%8E_LinkedList_%E7%9A%84%E5%8C%BA%E5%88%AB\"><\/span>ArrayDeque \u4e0e LinkedList \u7684\u533a\u522b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>ArrayDeque \u662f\u57fa\u4e8e\u53ef\u53d8\u957f\u7684\u6570\u7ec4\u548c\u53cc\u6307\u9488\u6765\u5b9e\u73b0\uff0c\u800c LinkedList \u5219\u901a\u8fc7\u94fe\u8868\u6765\u5b9e\u73b0\u3002<br \/>\nArrayDeque \u4e0d\u652f\u6301\u5b58\u50a8 NULL \u6570\u636e\uff0c\u4f46 LinkedList \u652f\u6301\u3002<br \/>\nArrayDeque \u662f\u5728 JDK1.6 \u624d\u88ab\u5f15\u5165\u7684\uff0c\u800cLinkedList \u65e9\u5728 JDK1.2 \u65f6\u5c31\u5df2\u7ecf\u5b58\u5728\u3002<br \/>\nArrayDeque \u63d2\u5165\u65f6\u53ef\u80fd\u5b58\u5728\u6269\u5bb9\u8fc7\u7a0b, \u4e0d\u8fc7\u5747\u644a\u540e\u7684\u63d2\u5165\u64cd\u4f5c\u4f9d\u7136\u4e3a O(1)\u3002\u867d\u7136 LinkedList \u4e0d\u9700\u8981\u6269\u5bb9\uff0c\u4f46\u662f\u6bcf\u6b21\u63d2\u5165\u6570\u636e\u65f6\u5747\u9700\u8981\u7533\u8bf7\u65b0\u7684\u5806\u7a7a\u95f4\uff0c\u5747\u644a\u6027\u80fd\u76f8\u6bd4\u66f4\u6162<\/p>\n<h3><span class=\"ez-toc-section\" id=\"HashMap_%E5%92%8C_Hashtable_%E7%9A%84%E5%8C%BA%E5%88%AB\"><\/span>HashMap \u548c Hashtable \u7684\u533a\u522b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><strong>\u7ebf\u7a0b\u662f\u5426\u5b89\u5168<\/strong>\uff1a HashMap \u662f\u975e\u7ebf\u7a0b\u5b89\u5168\u7684\uff0cHashtable \u662f\u7ebf\u7a0b\u5b89\u5168\u7684,\u56e0\u4e3a Hashtable \u5185\u90e8\u7684\u65b9\u6cd5\u57fa\u672c\u90fd\u7ecf\u8fc7synchronized \u4fee\u9970\u3002\uff08\u5982\u679c\u4f60\u8981\u4fdd\u8bc1\u7ebf\u7a0b\u5b89\u5168\u7684\u8bdd\u5c31\u4f7f\u7528 ConcurrentHashMap \u5427\uff01\uff09\uff1b<br \/>\n<strong>\u6548\u7387\uff1a<\/strong> \u56e0\u4e3a\u7ebf\u7a0b\u5b89\u5168\u7684\u95ee\u9898\uff0cHashMap \u8981\u6bd4 Hashtable \u6548\u7387\u9ad8\u4e00\u70b9\u3002\u53e6\u5916\uff0cHashtable \u57fa\u672c\u88ab\u6dd8\u6c70\uff0c\u4e0d\u8981\u5728\u4ee3\u7801\u4e2d\u4f7f\u7528\u5b83\uff1b<br \/>\n<strong>\u5bf9 Null key \u548c Null value \u7684\u652f\u6301<\/strong>\uff1a HashMap \u53ef\u4ee5\u5b58\u50a8 null \u7684 key \u548c value\uff0c\u4f46 null \u4f5c\u4e3a\u952e\u53ea\u80fd\u6709\u4e00\u4e2a\uff0cnull \u4f5c\u4e3a\u503c\u53ef\u4ee5\u6709\u591a\u4e2a\uff1bHashtable \u4e0d\u5141\u8bb8\u6709 null \u952e\u548c null \u503c\uff0c\u5426\u5219\u4f1a\u629b\u51faNullPointerException<br \/>\n<strong>\u521d\u59cb\u5bb9\u91cf\u5927\u5c0f\u548c\u6bcf\u6b21\u6269\u5145\u5bb9\u91cf\u5927\u5c0f\u7684\u4e0d\u540c<\/strong>\uff1a \u2460 \u521b\u5efa\u65f6\u5982\u679c\u4e0d\u6307\u5b9a\u5bb9\u91cf\u521d\u59cb\u503c\uff0cHashtable \u9ed8\u8ba4\u7684\u521d\u59cb\u5927\u5c0f\u4e3a 11\uff0c\u4e4b\u540e\u6bcf\u6b21\u6269\u5145\uff0c\u5bb9\u91cf\u53d8\u4e3a\u539f\u6765\u7684 2n+1\u3002HashMap \u9ed8\u8ba4\u7684\u521d\u59cb\u5316\u5927\u5c0f\u4e3a 16\u3002\u4e4b\u540e\u6bcf\u6b21\u6269\u5145\uff0c\u5bb9\u91cf\u53d8\u4e3a\u539f\u6765\u7684 2 \u500d\u3002\u2461 \u521b\u5efa\u65f6\u5982\u679c\u7ed9\u5b9a\u4e86\u5bb9\u91cf\u521d\u59cb\u503c\uff0c\u90a3\u4e48 Hashtable \u4f1a\u76f4\u63a5\u4f7f\u7528\u4f60\u7ed9\u5b9a\u7684\u5927\u5c0f\uff0c\u800c HashMap \u4f1a\u5c06\u5176\u6269\u5145\u4e3a 2 \u7684\u5e42\u6b21\u65b9\u5927\u5c0f\uff08HashMap \u4e2d\u7684tableSizeFor()\u65b9\u6cd5\u4fdd\u8bc1\uff0c\u4e0b\u9762\u7ed9\u51fa\u4e86\u6e90\u4ee3\u7801\uff09\u3002\u4e5f\u5c31\u662f\u8bf4 HashMap \u603b\u662f\u4f7f\u7528 2 \u7684\u5e42\u4f5c\u4e3a\u54c8\u5e0c\u8868\u7684\u5927\u5c0f,\u540e\u9762\u4f1a\u4ecb\u7ecd\u5230\u4e3a\u4ec0\u4e48\u662f 2 \u7684\u5e42\u6b21\u65b9\u3002<br \/>\n<strong>\u5e95\u5c42\u6570\u636e\u7ed3\u6784\uff1a<\/strong> JDK1.8 \u4ee5\u540e\u7684 HashMap \u5728\u89e3\u51b3\u54c8\u5e0c\u51b2\u7a81\u65f6\u6709\u4e86\u8f83\u5927\u7684\u53d8\u5316\uff0c\u5f53\u94fe\u8868\u957f\u5ea6\u5927\u4e8e\u9608\u503c\uff08\u9ed8\u8ba4\u4e3a 8\uff09\u65f6\uff0c\u5c06\u94fe\u8868\u8f6c\u5316\u4e3a\u7ea2\u9ed1\u6811\uff08\u5c06\u94fe\u8868\u8f6c\u6362\u6210\u7ea2\u9ed1\u6811\u524d\u4f1a\u5224\u65ad\uff0c\u5982\u679c\u5f53\u524d\u6570\u7ec4\u7684\u957f\u5ea6\u5c0f\u4e8e 64\uff0c\u90a3\u4e48\u4f1a\u9009\u62e9\u5148\u8fdb\u884c\u6570\u7ec4\u6269\u5bb9\uff0c\u800c\u4e0d\u662f\u8f6c\u6362\u4e3a\u7ea2\u9ed1\u6811\uff09\uff0c\u4ee5\u51cf\u5c11\u641c\u7d22\u65f6\u95f4\uff08\u540e\u6587\u4e2d\u6211\u4f1a\u7ed3\u5408\u6e90\u7801\u5bf9\u8fd9\u4e00\u8fc7\u7a0b\u8fdb\u884c\u5206\u6790\uff09\u3002Hashtable \u6ca1\u6709\u8fd9\u6837\u7684\u673a\u5236\u3002<br \/>\n<strong>\u54c8\u5e0c\u51fd\u6570\u7684\u5b9e\u73b0<\/strong>\uff1aHashMap \u5bf9\u54c8\u5e0c\u503c\u8fdb\u884c\u4e86\u9ad8\u4f4d\u548c\u4f4e\u4f4d\u7684\u6df7\u5408\u6270\u52a8\u5904\u7406\u4ee5\u51cf\u5c11\u51b2\u7a81\uff0c\u800c Hashtable \u76f4\u63a5\u4f7f\u7528\u952e\u7684 hashCode() \u503c\u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"HashMap_%E5%92%8C_HashSet_%E5%8C%BA%E5%88%AB\"><\/span>HashMap \u548c HashSet \u533a\u522b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>\u5982\u679c\u4f60\u770b\u8fc7 HashSet \u6e90\u7801\u7684\u8bdd\u5c31\u5e94\u8be5\u77e5\u9053\uff1aHashSet \u5e95\u5c42\u5c31\u662f\u57fa\u4e8e HashMap \u5b9e\u73b0\u7684\u3002\uff08HashSet \u7684\u6e90\u7801\u975e\u5e38\u975e\u5e38\u5c11\uff0c\u56e0\u4e3a\u9664\u4e86 clone()\u3001writeObject()\u3001readObject()\u662f HashSet \u81ea\u5df1\u4e0d\u5f97\u4e0d\u5b9e\u73b0\u4e4b\u5916\uff0c\u5176\u4ed6\u65b9\u6cd5\u90fd\u662f\u76f4\u63a5\u8c03\u7528 HashMap \u4e2d\u7684\u65b9\u6cd5\u3002<br \/>\n<img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752325875038.png\" alt=\"file\" \/><\/p>\n<h3><span class=\"ez-toc-section\" id=\"HashMap_%E5%92%8C_TreeMap_%E5%8C%BA%E5%88%AB\"><\/span>HashMap \u548c TreeMap \u533a\u522b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>TreeMap \u548cHashMap \u90fd\u7ee7\u627f\u81eaAbstractMap \uff0c\u4f46\u662f\u9700\u8981\u6ce8\u610f\u7684\u662fTreeMap\u5b83\u8fd8\u5b9e\u73b0\u4e86NavigableMap\u63a5\u53e3\u548cSortedMap \u63a5\u53e3\u3002<br \/>\n<img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752325896410.png\" alt=\"file\" \/><\/p>\n<p>\u5b9e\u73b0 NavigableMap \u63a5\u53e3\u8ba9 TreeMap \u6709\u4e86\u5bf9\u96c6\u5408\u5185\u5143\u7d20\u7684\u641c\u7d22\u7684\u80fd\u529b\u3002<\/p>\n<p>NavigableMap \u63a5\u53e3\u63d0\u4f9b\u4e86\u4e30\u5bcc\u7684\u65b9\u6cd5\u6765\u63a2\u7d22\u548c\u64cd\u4f5c\u952e\u503c\u5bf9:<br \/>\n<strong>\u5b9a\u5411\u641c\u7d22<\/strong>: ceilingEntry(), floorEntry(), higherEntry()\u548c lowerEntry() \u7b49\u65b9\u6cd5\u53ef\u4ee5\u7528\u4e8e\u5b9a\u4f4d\u5927\u4e8e\u7b49\u4e8e\u3001\u5c0f\u4e8e\u7b49\u4e8e\u3001\u4e25\u683c\u5927\u4e8e\u3001\u4e25\u683c\u5c0f\u4e8e\u7ed9\u5b9a\u952e\u7684\u6700\u63a5\u8fd1\u7684\u952e\u503c\u5bf9\u3002<br \/>\n<strong>\u5b50\u96c6\u64cd\u4f5c<\/strong>: subMap(), headMap()\u548c tailMap() \u65b9\u6cd5\u53ef\u4ee5\u9ad8\u6548\u5730\u521b\u5efa\u539f\u96c6\u5408\u7684\u5b50\u96c6\u89c6\u56fe\uff0c\u800c\u65e0\u9700\u590d\u5236\u6574\u4e2a\u96c6\u5408\u3002<br \/>\n<strong>\u9006\u5e8f\u89c6\u56fe<\/strong>:descendingMap() \u65b9\u6cd5\u8fd4\u56de\u4e00\u4e2a\u9006\u5e8f\u7684 NavigableMap \u89c6\u56fe\uff0c\u4f7f\u5f97\u53ef\u4ee5\u53cd\u5411\u8fed\u4ee3\u6574\u4e2a TreeMap\u3002<br \/>\n<strong>\u8fb9\u754c\u64cd\u4f5c<\/strong>: firstEntry(), lastEntry(), pollFirstEntry()\u548c pollLastEntry() \u7b49\u65b9\u6cd5\u53ef\u4ee5\u65b9\u4fbf\u5730\u8bbf\u95ee\u548c\u79fb\u9664\u5143\u7d20\u3002<\/p>\n<p>\u8fd9\u4e9b\u65b9\u6cd5\u90fd\u662f\u57fa\u4e8e\u7ea2\u9ed1\u6811\u6570\u636e\u7ed3\u6784\u7684\u5c5e\u6027\u5b9e\u73b0\u7684\uff0c\u7ea2\u9ed1\u6811\u4fdd\u6301\u5e73\u8861\u72b6\u6001\uff0c\u4ece\u800c\u4fdd\u8bc1\u4e86\u641c\u7d22\u64cd\u4f5c\u7684\u65f6\u95f4\u590d\u6742\u5ea6\u4e3a O(log n)\uff0c\u8fd9\u8ba9 TreeMap \u6210\u4e3a\u4e86\u5904\u7406\u6709\u5e8f\u96c6\u5408\u641c\u7d22\u95ee\u9898\u7684\u5f3a\u5927\u5de5\u5177\u3002\u5b9e\u73b0SortedMap\u63a5\u53e3\u8ba9 TreeMap \u6709\u4e86\u5bf9\u96c6\u5408\u4e2d\u7684\u5143\u7d20\u6839\u636e\u952e\u6392\u5e8f\u7684\u80fd\u529b\u3002\u9ed8\u8ba4\u662f\u6309 key \u7684\u5347\u5e8f\u6392\u5e8f\uff0c\u4e0d\u8fc7\u6211\u4eec\u4e5f\u53ef\u4ee5\u6307\u5b9a\u6392\u5e8f\u7684\u6bd4\u8f83\u5668\u3002\u793a\u4f8b\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">\npublic class Person {\n    private Integer age;\n\n    public Person(Integer age) {\n        this.age = age;\n    }\n\n    public Integer getAge() {\n        return age;\n    }\n\n    public static void main(String[] args) {\n        TreeMap&lt;Person, String&gt; treeMap = new TreeMap&lt;&gt;(new Comparator&lt;Person&gt;() {\n            @Override\n            public int compare(Person person1, Person person2) {\n                int num = person1.getAge() - person2.getAge();\n                return Integer.compare(num, 0);\n            }\n        });\n        treeMap.put(new Person(3), &quot;person1&quot;);\n        treeMap.put(new Person(18), &quot;person2&quot;);\n        treeMap.put(new Person(35), &quot;person3&quot;);\n        treeMap.put(new Person(16), &quot;person4&quot;);\n        treeMap.entrySet().stream().forEach(personStringEntry -&gt; {\n            System.out.println(personStringEntry.getValue());\n        });\n    }\n}\n\u8f93\u51fa:\nperson1\nperson4\nperson2\nperson3<\/code><\/pre>\n<p>\u53ef\u4ee5\u770b\u51fa\uff0cTreeMap \u4e2d\u7684\u5143\u7d20\u5df2\u7ecf\u662f\u6309\u7167 Person \u7684 age \u5b57\u6bb5\u7684\u5347\u5e8f\u6765\u6392\u5217\u4e86\u3002<br \/>\n\u4e0a\u9762\uff0c\u6211\u4eec\u662f\u901a\u8fc7\u4f20\u5165\u533f\u540d\u5185\u90e8\u7c7b\u7684\u65b9\u5f0f\u5b9e\u73b0\u7684\uff0c\u4f60\u53ef\u4ee5\u5c06\u4ee3\u7801\u66ff\u6362\u6210 Lambda \u8868\u8fbe\u5f0f\u5b9e\u73b0\u7684\u65b9\u5f0f\uff1a<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">TreeMap&lt;Person, String&gt; treeMap = new TreeMap&lt;&gt;((person1, person2) -&gt; {\n  int num = person1.getAge() - person2.getAge();\n  return Integer.compare(num, 0);\n});<\/code><\/pre>\n<p><strong>\u7efc\u4e0a\uff0c\u76f8\u6bd4\u4e8eHashMap\u6765\u8bf4\uff0c TreeMap \u4e3b\u8981\u591a\u4e86\u5bf9\u96c6\u5408\u4e2d\u7684\u5143\u7d20\u6839\u636e\u952e\u6392\u5e8f\u7684\u80fd\u529b\u4ee5\u53ca\u5bf9\u96c6\u5408\u5185\u5143\u7d20\u7684\u641c\u7d22\u7684\u80fd\u529b<\/strong><\/p>\n<h3><span class=\"ez-toc-section\" id=\"HashSet_%E5%A6%82%E4%BD%95%E6%A3%80%E6%9F%A5%E9%87%8D%E5%A4%8D\"><\/span>HashSet \u5982\u4f55\u68c0\u67e5\u91cd\u590d?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>\u5728 JDK1.8 \u4e2d\uff0cHashSet\u7684add()\u65b9\u6cd5\u53ea\u662f\u7b80\u5355\u7684\u8c03\u7528\u4e86HashMap\u7684put()\u65b9\u6cd5\uff0c\u5e76\u4e14\u5224\u65ad\u4e86\u4e00\u4e0b\u8fd4\u56de\u503c\u4ee5\u786e\u4fdd\u662f\u5426\u6709\u91cd\u590d\u5143\u7d20\u3002\u76f4\u63a5\u770b\u4e00\u4e0bHashSet\u4e2d\u7684\u6e90\u7801\uff1a<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">\/\/ Returns: true if this set did not already contain the specified element\n\/\/ \u8fd4\u56de\u503c\uff1a\u5f53 set \u4e2d\u6ca1\u6709\u5305\u542b add \u7684\u5143\u7d20\u65f6\u8fd4\u56de\u771f\npublic boolean add(E e) {\n        return map.put(e, PRESENT)==null;\n}<\/code><\/pre>\n<p>\u800c\u5728HashMap\u7684putVal()\u65b9\u6cd5\u4e2d\u4e5f\u80fd\u770b\u5230\u5982\u4e0b\u8bf4\u660e\uff1a<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">\/\/ Returns : previous value, or null if none\n\/\/ \u8fd4\u56de\u503c\uff1a\u5982\u679c\u63d2\u5165\u4f4d\u7f6e\u6ca1\u6709\u5143\u7d20\u8fd4\u56denull\uff0c\u5426\u5219\u8fd4\u56de\u4e0a\u4e00\u4e2a\u5143\u7d20\nfinal V putVal(int hash, K key, V value, boolean onlyIfAbsent,\n                   boolean evict) {\n...\n}<\/code><\/pre>\n<p><strong>\u4e5f\u5c31\u662f\u8bf4\uff0c\u5728 JDK1.8 \u4e2d\uff0c\u5b9e\u9645\u4e0a\u65e0\u8bbaHashSet\u4e2d\u662f\u5426\u5df2\u7ecf\u5b58\u5728\u4e86\u67d0\u5143\u7d20\uff0cHashSet\u90fd\u4f1a\u76f4\u63a5\u63d2\u5165\uff0c\u53ea\u662f\u4f1a\u5728add()\u65b9\u6cd5\u7684\u8fd4\u56de\u503c\u5904\u544a\u8bc9\u6211\u4eec\u63d2\u5165\u524d\u662f\u5426\u5b58\u5728\u76f8\u540c\u5143\u7d20<\/strong><\/p>\n<h3><span class=\"ez-toc-section\" id=\"HashMap_%E7%9A%84%E5%BA%95%E5%B1%82%E5%AE%9E%E7%8E%B0\"><\/span>HashMap \u7684\u5e95\u5c42\u5b9e\u73b0<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>JDK1.8 \u4e4b\u524d HashMap \u5e95\u5c42\u662f <strong>\u6570\u7ec4\u548c\u94fe\u8868<\/strong> \u7ed3\u5408\u5728\u4e00\u8d77\u4f7f\u7528\u4e5f\u5c31\u662f <strong>\u94fe\u8868\u6563\u5217<\/strong>\u3002HashMap \u901a\u8fc7 key \u7684 hashcode \u7ecf\u8fc7\u6270\u52a8\u51fd\u6570\u5904\u7406\u8fc7\u540e\u5f97\u5230 hash \u503c\uff0c\u7136\u540e\u901a\u8fc7 (n - 1) &amp; hash \u5224\u65ad\u5f53\u524d\u5143\u7d20\u5b58\u653e\u7684\u4f4d\u7f6e\uff08\u8fd9\u91cc\u7684 n \u6307\u7684\u662f\u6570\u7ec4\u7684\u957f\u5ea6\uff09\uff0c\u5982\u679c\u5f53\u524d\u4f4d\u7f6e\u5b58\u5728\u5143\u7d20\u7684\u8bdd\uff0c\u5c31\u5224\u65ad\u8be5\u5143\u7d20\u4e0e\u8981\u5b58\u5165\u7684\u5143\u7d20\u7684 hash \u503c\u4ee5\u53ca key \u662f\u5426\u76f8\u540c\uff0c\u5982\u679c\u76f8\u540c\u7684\u8bdd\uff0c\u76f4\u63a5\u8986\u76d6\uff0c\u4e0d\u76f8\u540c\u5c31\u901a\u8fc7\u62c9\u94fe\u6cd5\u89e3\u51b3\u51b2\u7a81\u3002<br \/>\nHashMap \u4e2d\u7684\u6270\u52a8\u51fd\u6570\uff08hash \u65b9\u6cd5\uff09\u662f\u7528\u6765\u4f18\u5316\u54c8\u5e0c\u503c\u7684\u5206\u5e03\u3002\u901a\u8fc7\u5bf9\u539f\u59cb\u7684 hashCode() \u8fdb\u884c\u989d\u5916\u5904\u7406\uff0c\u6270\u52a8\u51fd\u6570\u53ef\u4ee5\u51cf\u5c0f\u7531\u4e8e\u7cdf\u7cd5\u7684 hashCode() \u5b9e\u73b0\u5bfc\u81f4\u7684\u78b0\u649e\uff0c\u4ece\u800c\u63d0\u9ad8\u6570\u636e\u7684\u5206\u5e03\u5747\u5300\u6027\u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"JDK_18_HashMap_%E7%9A%84_hash_%E6%96%B9%E6%B3%95%E6%BA%90%E7%A0%81\"><\/span>JDK 1.8 HashMap \u7684 hash \u65b9\u6cd5\u6e90\u7801:<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">JDK 1.8 \u7684 hash \u65b9\u6cd5 \u76f8\u6bd4\u4e8e JDK 1.7 hash \u65b9\u6cd5\u66f4\u52a0\u7b80\u5316\uff0c\u4f46\u662f\u539f\u7406\u4e0d\u53d8\u3002\n    static final int hash(Object key) {\n      int h;\n      \/\/ key.hashCode()\uff1a\u8fd4\u56de\u6563\u5217\u503c\u4e5f\u5c31\u662fhashcode\n      \/\/ ^\uff1a\u6309\u4f4d\u5f02\u6216\n      \/\/ &gt;&gt;&gt;:\u65e0\u7b26\u53f7\u53f3\u79fb\uff0c\u5ffd\u7565\u7b26\u53f7\u4f4d\uff0c\u7a7a\u4f4d\u90fd\u4ee50\u8865\u9f50\n      return (key == null) ? 0 : (h = key.hashCode()) ^ (h &gt;&gt;&gt; 16);\n  }\n\u5bf9\u6bd4\u4e00\u4e0b JDK1.7 \u7684 HashMap \u7684 hash \u65b9\u6cd5\u6e90\u7801\nstatic int hash(int h) {\n    \/\/ This function ensures that hashCodes that differ only by\n    \/\/ constant multiples at each bit position have a bounded\n    \/\/ number of collisions (approximately 8 at default load factor).\n\n    h ^= (h &gt;&gt;&gt; 20) ^ (h &gt;&gt;&gt; 12);\n    return h ^ (h &gt;&gt;&gt; 7) ^ (h &gt;&gt;&gt; 4);\n}\n\u76f8\u6bd4\u4e8e JDK1.8 \u7684 hash \u65b9\u6cd5 \uff0cJDK 1.7 \u7684 hash \u65b9\u6cd5\u7684\u6027\u80fd\u4f1a\u7a0d\u5dee\u4e00\u70b9\u70b9\uff0c\u56e0\u4e3a\u6bd5\u7adf\u6270\u52a8\u4e86 4 \u6b21\u3002<\/code><\/pre>\n<p>\u6240\u8c13 \u201c<strong>\u62c9\u94fe\u6cd5<\/strong>\u201d \u5c31\u662f\uff1a\u5c06\u94fe\u8868\u548c\u6570\u7ec4\u76f8\u7ed3\u5408\u3002\u4e5f\u5c31\u662f\u8bf4\u521b\u5efa\u4e00\u4e2a\u94fe\u8868\u6570\u7ec4\uff0c\u6570\u7ec4\u4e2d\u6bcf\u4e00\u683c\u5c31\u662f\u4e00\u4e2a\u94fe\u8868\u3002\u82e5\u9047\u5230\u54c8\u5e0c\u51b2\u7a81\uff0c\u5219\u5c06\u51b2\u7a81\u7684\u503c\u52a0\u5230\u94fe\u8868\u4e2d\u5373\u53ef\u3002<br \/>\n<img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752326301016.png\" alt=\"file\" \/><\/p>\n<p>JDK1.8 \u4e4b\u540e\u76f8\u6bd4\u4e8e\u4e4b\u524d\u7684\u7248\u672c\uff0c JDK1.8 \u4e4b\u540e\u5728\u89e3\u51b3\u54c8\u5e0c\u51b2\u7a81\u65f6\u6709\u4e86\u8f83\u5927\u7684\u53d8\u5316\uff0c\u5f53\u94fe\u8868\u957f\u5ea6\u5927\u4e8e\u9608\u503c\uff08\u9ed8\u8ba4\u4e3a 8\uff09\uff08\u5c06\u94fe\u8868\u8f6c\u6362\u6210\u7ea2\u9ed1\u6811\u524d\u4f1a\u5224\u65ad\uff0c\u5982\u679c\u5f53\u524d\u6570\u7ec4\u7684\u957f\u5ea6\u5c0f\u4e8e 64\uff0c\u90a3\u4e48\u4f1a\u9009\u62e9\u5148\u8fdb\u884c\u6570\u7ec4\u6269\u5bb9\uff0c\u800c\u4e0d\u662f\u8f6c\u6362\u4e3a\u7ea2\u9ed1\u6811\uff09\u65f6\uff0c\u5c06\u94fe\u8868\u8f6c\u5316\u4e3a\u7ea2\u9ed1\u6811\u3002<br \/>\n\u8fd9\u6837\u505a\u7684\u76ee\u7684\u662f\u51cf\u5c11\u641c\u7d22\u65f6\u95f4\uff1a\u94fe\u8868\u7684\u67e5\u8be2\u6548\u7387\u4e3a O(n)\uff08n \u662f\u94fe\u8868\u7684\u957f\u5ea6\uff09\uff0c\u7ea2\u9ed1\u6811\u662f\u4e00\u79cd\u81ea\u5e73\u8861\u4e8c\u53c9\u641c\u7d22\u6811\uff0c\u5176\u67e5\u8be2\u6548\u7387\u4e3a O(log n)\u3002\u5f53\u94fe\u8868\u8f83\u77ed\u65f6\uff0cO(n) \u548c O(log n) \u7684\u6027\u80fd\u5dee\u5f02\u4e0d\u660e\u663e\u3002\u4f46\u5f53\u94fe\u8868\u53d8\u957f\u65f6\uff0c\u67e5\u8be2\u6027\u80fd\u4f1a\u663e\u8457\u4e0b\u964d\u3002<br \/>\n<img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752326350094.png\" alt=\"file\" \/><\/p>\n<h3><span class=\"ez-toc-section\" id=\"%E4%B8%BA%E4%BB%80%E4%B9%88%E4%BC%98%E5%85%88%E6%89%A9%E5%AE%B9%E8%80%8C%E9%9D%9E%E7%9B%B4%E6%8E%A5%E8%BD%AC%E4%B8%BA%E7%BA%A2%E9%BB%91%E6%A0%91%EF%BC%9F\"><\/span>\u4e3a\u4ec0\u4e48\u4f18\u5148\u6269\u5bb9\u800c\u975e\u76f4\u63a5\u8f6c\u4e3a\u7ea2\u9ed1\u6811\uff1f<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>1\u3001\u6570\u7ec4\u6269\u5bb9\u80fd\u51cf\u5c11\u54c8\u5e0c\u51b2\u7a81\u7684\u53d1\u751f\u6982\u7387\uff08\u5373\u5c06\u5143\u7d20\u91cd\u65b0\u5206\u6563\u5230\u65b0\u7684\u3001\u66f4\u5927\u7684\u6570\u7ec4\u4e2d\uff09\uff0c\u8fd9\u5728\u591a\u6570\u60c5\u51b5\u4e0b\u6bd4\u76f4\u63a5\u8f6c\u6362\u4e3a\u7ea2\u9ed1\u6811\u66f4\u9ad8\u6548\u3002<br \/>\n2\u3001\u7ea2\u9ed1\u6811\u9700\u8981\u4fdd\u6301\u81ea\u5e73\u8861\uff0c\u7ef4\u62a4\u6210\u672c\u8f83\u9ad8\u3002\u5e76\u4e14\uff0c\u8fc7\u65e9\u5f15\u5165\u7ea2\u9ed1\u6811\u53cd\u800c\u4f1a\u589e\u52a0\u590d\u6742\u5ea6\u3002<\/p>\n<h4><span class=\"ez-toc-section\" id=\"%E4%B8%BA%E4%BB%80%E4%B9%88%E9%80%89%E6%8B%A9%E9%98%88%E5%80%BC_8_%E5%92%8C_64%EF%BC%9F\"><\/span>\u4e3a\u4ec0\u4e48\u9009\u62e9\u9608\u503c 8 \u548c 64\uff1f<span class=\"ez-toc-section-end\"><\/span><\/h4>\n<p>1\u3001\u6cca\u677e\u5206\u5e03\u8868\u660e\uff0c\u94fe\u8868\u957f\u5ea6\u8fbe\u5230 8 \u7684\u6982\u7387\u6781\u4f4e\uff08\u5c0f\u4e8e\u5343\u4e07\u5206\u4e4b\u4e00\uff09\u3002\u5728\u7edd\u5927\u591a\u6570\u60c5\u51b5\u4e0b\uff0c\u94fe\u8868\u957f\u5ea6\u90fd\u4e0d\u4f1a\u8d85\u8fc7 8\u3002\u9608\u503c\u8bbe\u7f6e\u4e3a 8\uff0c\u53ef\u4ee5\u4fdd\u8bc1\u6027\u80fd\u548c\u7a7a\u95f4\u6548\u7387\u7684\u5e73\u8861\u3002<br \/>\n2\u3001\u6570\u7ec4\u957f\u5ea6\u9608\u503c 64 \u540c\u6837\u662f\u7ecf\u8fc7\u5b9e\u8df5\u9a8c\u8bc1\u7684\u7ecf\u9a8c\u503c\u3002\u5728\u5c0f\u6570\u7ec4\u4e2d\u6269\u5bb9\u6210\u672c\u4f4e\uff0c\u4f18\u5148\u6269\u5bb9\u53ef\u4ee5\u907f\u514d\u8fc7\u65e9\u5f15\u5165\u7ea2\u9ed1\u6811\u3002\u6570\u7ec4\u5927\u5c0f\u8fbe\u5230 64 \u65f6\uff0c\u51b2\u7a81\u6982\u7387\u8f83\u9ad8\uff0c\u6b64\u65f6\u7ea2\u9ed1\u6811\u7684\u6027\u80fd\u4f18\u52bf\u5f00\u59cb\u663e\u73b0\u3002<br \/>\n<img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752326428433.png\" alt=\"file\" \/><\/p>\n<h3><span class=\"ez-toc-section\" id=\"%E6%88%91%E4%BB%AC%E6%9D%A5%E7%BB%93%E5%90%88%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90%E4%B8%80%E4%B8%8B_HashMap_%E9%93%BE%E8%A1%A8%E5%88%B0%E7%BA%A2%E9%BB%91%E6%A0%91%E7%9A%84%E8%BD%AC%E6%8D%A2\"><\/span>\u6211\u4eec\u6765\u7ed3\u5408\u6e90\u7801\u5206\u6790\u4e00\u4e0b HashMap \u94fe\u8868\u5230\u7ea2\u9ed1\u6811\u7684\u8f6c\u6362<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">1\u3001 putVal \u65b9\u6cd5\u4e2d\u6267\u884c\u94fe\u8868\u8f6c\u7ea2\u9ed1\u6811\u7684\u5224\u65ad\u903b\u8f91\u3002\n\n\u94fe\u8868\u7684\u957f\u5ea6\u5927\u4e8e 8 \u7684\u65f6\u5019\uff0c\u5c31\u6267\u884c treeifyBin \uff08\u8f6c\u6362\u7ea2\u9ed1\u6811\uff09\u7684\u903b\u8f91\u3002\n\/\/ \u904d\u5386\u94fe\u8868\nfor (int binCount = 0; ; ++binCount) {\n    \/\/ \u904d\u5386\u5230\u94fe\u8868\u6700\u540e\u4e00\u4e2a\u8282\u70b9\n    if ((e = p.next) == null) {\n        p.next = newNode(hash, key, value, null);\n        \/\/ \u5982\u679c\u94fe\u8868\u5143\u7d20\u4e2a\u6570\u5927\u4e8eTREEIFY_THRESHOLD\uff088\uff09\n        if (binCount &gt;= TREEIFY_THRESHOLD - 1) \/\/ -1 for 1st\n            \/\/ \u7ea2\u9ed1\u6811\u8f6c\u6362\uff08\u5e76\u4e0d\u4f1a\u76f4\u63a5\u8f6c\u6362\u6210\u7ea2\u9ed1\u6811\uff09\n            treeifyBin(tab, hash);\n        break;\n    }\n    if (e.hash == hash &amp;&amp;\n        ((k = e.key) == key || (key != null &amp;&amp; key.equals(k))))\n        break;\n    p = e;\n}\n\n2\u3001treeifyBin \u65b9\u6cd5\u4e2d\u5224\u65ad\u662f\u5426\u771f\u7684\u8f6c\u6362\u4e3a\u7ea2\u9ed1\u6811\u3002\nfinal void treeifyBin(Node&lt;K,V&gt;[] tab, int hash) {\n    int n, index; Node&lt;K,V&gt; e;\n    \/\/ \u5224\u65ad\u5f53\u524d\u6570\u7ec4\u7684\u957f\u5ea6\u662f\u5426\u5c0f\u4e8e 64\n    if (tab == null || (n = tab.length) &lt; MIN_TREEIFY_CAPACITY)\n        \/\/ \u5982\u679c\u5f53\u524d\u6570\u7ec4\u7684\u957f\u5ea6\u5c0f\u4e8e 64\uff0c\u90a3\u4e48\u4f1a\u9009\u62e9\u5148\u8fdb\u884c\u6570\u7ec4\u6269\u5bb9\n        resize();\n    else if ((e = tab[index = (n - 1) &amp; hash]) != null) {\n        \/\/ \u5426\u5219\u624d\u5c06\u5217\u8868\u8f6c\u6362\u4e3a\u7ea2\u9ed1\u6811\n\n        TreeNode&lt;K,V&gt; hd = null, tl = null;\n        do {\n            TreeNode&lt;K,V&gt; p = replacementTreeNode(e, null);\n            if (tl == null)\n                hd = p;\n            else {\n                p.prev = tl;\n                tl.next = p;\n            }\n            tl = p;\n        } while ((e = e.next) != null);\n        if ((tab[index] = hd) != null)\n            hd.treeify(tab);\n    }\n}\n\n\u5c06\u94fe\u8868\u8f6c\u6362\u6210\u7ea2\u9ed1\u6811\u524d\u4f1a\u5224\u65ad\uff0c\u5982\u679c\u5f53\u524d\u6570\u7ec4\u7684\u957f\u5ea6\u5c0f\u4e8e 64\uff0c\u90a3\u4e48\u4f1a\u9009\u62e9\u5148\u8fdb\u884c\u6570\u7ec4\u6269\u5bb9\uff0c\u800c\u4e0d\u662f\u8f6c\u6362\u4e3a\u7ea2\u9ed1\u6811\u3002<\/code><\/pre>\n<h3><span class=\"ez-toc-section\" id=\"HashMap_%E7%9A%84%E9%95%BF%E5%BA%A6%E4%B8%BA%E4%BB%80%E4%B9%88%E6%98%AF_2_%E7%9A%84%E5%B9%82%E6%AC%A1%E6%96%B9\"><\/span>HashMap \u7684\u957f\u5ea6\u4e3a\u4ec0\u4e48\u662f 2 \u7684\u5e42\u6b21\u65b9<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>\u4e3a\u4e86\u8ba9 HashMap \u5b58\u53d6\u9ad8\u6548\u5e76\u51cf\u5c11\u78b0\u649e\uff0c\u6211\u4eec\u9700\u8981\u786e\u4fdd\u6570\u636e\u5c3d\u91cf\u5747\u5300\u5206\u5e03\u3002\u54c8\u5e0c\u503c\u5728 Java \u4e2d\u901a\u5e38\u4f7f\u7528 int \u8868\u793a\uff0c\u5176\u8303\u56f4\u662f -2147483648 ~ 2147483647\u524d\u540e\u52a0\u8d77\u6765\u5927\u6982 40 \u4ebf\u7684\u6620\u5c04\u7a7a\u95f4\uff0c\u53ea\u8981\u54c8\u5e0c\u51fd\u6570\u6620\u5c04\u5f97\u6bd4\u8f83\u5747\u5300\u677e\u6563\uff0c\u4e00\u822c\u5e94\u7528\u662f\u5f88\u96be\u51fa\u73b0\u78b0\u649e\u7684\u3002\u4f46\u662f\uff0c\u95ee\u9898\u662f\u4e00\u4e2a 40 \u4ebf\u957f\u5ea6\u7684\u6570\u7ec4\uff0c\u5185\u5b58\u662f\u653e\u4e0d\u4e0b\u7684\u3002\u6240\u4ee5\uff0c\u8fd9\u4e2a\u6563\u5217\u503c\u662f\u4e0d\u80fd\u76f4\u63a5\u62ff\u6765\u7528\u7684\u3002\u7528\u4e4b\u524d\u8fd8\u8981\u5148\u505a\u5bf9\u6570\u7ec4\u7684\u957f\u5ea6\u53d6\u6a21\u8fd0\u7b97\uff0c\u5f97\u5230\u7684\u4f59\u6570\u624d\u80fd\u7528\u6765\u8981\u5b58\u653e\u7684\u4f4d\u7f6e\u4e5f\u5c31\u662f\u5bf9\u5e94\u7684\u6570\u7ec4\u4e0b\u6807\u3002<\/p>\n<p>\u6211\u4eec\u9996\u5148\u53ef\u80fd\u4f1a\u60f3\u5230\u91c7\u7528 % \u53d6\u4f59\u7684\u64cd\u4f5c\u6765\u5b9e\u73b0\u3002\u4f46\u662f\uff0c\u91cd\u70b9\u6765\u4e86\uff1a\u201c<strong>\u53d6\u4f59(%)\u64cd\u4f5c\u4e2d\u5982\u679c\u9664\u6570\u662f 2 \u7684\u5e42\u6b21\u5219\u7b49\u4ef7\u4e8e\u4e0e\u5176\u9664\u6570\u51cf\u4e00\u7684\u4e0e(&amp;)\u64cd\u4f5c<\/strong>\uff08\u4e5f\u5c31\u662f\u8bf4 hash%length==hash&amp;(length-1) \u7684\u524d\u63d0\u662f length \u662f 2 \u7684 n \u6b21\u65b9\uff09\u3002\u201d \u5e76\u4e14\uff0c<strong>\u91c7\u7528\u4e8c\u8fdb\u5236\u4f4d\u64cd\u4f5c &amp; \u76f8\u5bf9\u4e8e % \u80fd\u591f\u63d0\u9ad8\u8fd0\u7b97\u6548\u7387<\/strong><\/p>\n<p>\u9664\u4e86\u4e0a\u9762\u6240\u8bf4\u7684\u4f4d\u8fd0\u7b97\u6bd4\u53d6\u4f59\u6548\u7387\u9ad8\u4e4b\u5916\uff0c\u6211\u89c9\u5f97\u66f4\u91cd\u8981\u7684\u4e00\u4e2a\u539f\u56e0\u662f\uff1a\u957f\u5ea6\u662f 2 \u7684\u5e42\u6b21\u65b9\uff0c\u53ef\u4ee5\u8ba9 HashMap \u5728\u6269\u5bb9\u7684\u65f6\u5019\u66f4\u5747\u5300\u3002\u4f8b\u5982:<br \/>\nlength = 8 \u65f6\uff0clength - 1 = 7 \u7684\u4e8c\u8fdb\u5236\u4f4d0111<br \/>\nlength = 16 \u65f6\uff0clength - 1 = 15 \u7684\u4e8c\u8fdb\u5236\u4f4d1111<br \/>\n\u8fd9\u65f6\u5019\u539f\u672c\u5b58\u5728 HashMap \u4e2d\u7684\u5143\u7d20\u8ba1\u7b97\u65b0\u7684\u6570\u7ec4\u4f4d\u7f6e\u65f6 hash&amp;(length-1)\uff0c\u53d6\u51b3 hash \u7684\u7b2c\u56db\u4e2a\u4e8c\u8fdb\u5236\u4f4d\uff08\u4ece\u53f3\u6570\uff09\uff0c\u4f1a\u51fa\u73b0\u4e24\u79cd\u60c5\u51b5\uff1a<br \/>\n\u7b2c\u56db\u4e2a\u4e8c\u8fdb\u5236\u4f4d\u4e3a 0\uff0c\u6570\u7ec4\u4f4d\u7f6e\u4e0d\u53d8\uff0c\u4e5f\u5c31\u662f\u8bf4\u5f53\u524d\u5143\u7d20\u5728\u65b0\u6570\u7ec4\u548c\u65e7\u6570\u7ec4\u7684\u4f4d\u7f6e\u76f8\u540c\u3002<br \/>\n\u7b2c\u56db\u4e2a\u4e8c\u8fdb\u5236\u4f4d\u4e3a 1\uff0c\u6570\u7ec4\u4f4d\u7f6e\u5728\u65b0\u6570\u7ec4\u6269\u5bb9\u4e4b\u540e\u7684\u90a3\u4e00\u90e8\u5206\u3002<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">\u5047\u8bbe\u6709\u4e00\u4e2a\u5143\u7d20\u7684\u54c8\u5e0c\u503c\u4e3a 10101100\n\n\u65e7\u6570\u7ec4\u5143\u7d20\u4f4d\u7f6e\u8ba1\u7b97\uff1a\nhash        = 10101100\nlength - 1  = 00000111\n&amp; -----------------\nindex       = 00000100  (4)\n\n\u65b0\u6570\u7ec4\u5143\u7d20\u4f4d\u7f6e\u8ba1\u7b97\uff1a\nhash        = 10101100\nlength - 1  = 00001111\n&amp; -----------------\nindex       = 00001100  (12)\n\n\u770b\u7b2c\u56db\u4f4d\uff08\u4ece\u53f3\u6570\uff09\uff1a\n1.\u9ad8\u4f4d\u4e3a 0\uff1a\u4f4d\u7f6e\u4e0d\u53d8\u3002\n2.\u9ad8\u4f4d\u4e3a 1\uff1a\u79fb\u52a8\u5230\u65b0\u4f4d\u7f6e\uff08\u539f\u7d22\u5f15\u4f4d\u7f6e+\u539f\u5bb9\u91cf\uff09\u3002<\/code><\/pre>\n<p>\u6ce8\u610f\uff1a\u8fd9\u91cc\u5217\u4e3e\u7684\u573a\u666f\u770b\u7684\u662f\u7b2c\u56db\u4e2a\u4e8c\u8fdb\u5236\u4f4d\uff0c\u66f4\u51c6\u786e\u70b9\u6765\u8bf4\u770b\u7684\u662f\u9ad8\u4f4d\uff08\u4ece\u53f3\u6570\uff09\uff0c\u4f8b\u5982 length = 32 \u65f6\uff0clength - 1 = 31\uff0c\u4e8c\u8fdb\u5236\u4e3a 11111\uff0c\u8fd9\u91cc\u770b\u7684\u5c31\u662f\u7b2c\u4e94\u4e2a\u4e8c\u8fdb\u5236\u4f4d\u3002<br \/>\n\u4e5f\u5c31\u662f\u8bf4\u6269\u5bb9\u4e4b\u540e\uff0c\u5728\u65e7\u6570\u7ec4\u5143\u7d20 hash \u503c\u6bd4\u8f83\u5747\u5300\uff08\u81f3\u4e8e hash \u503c\u5747\u4e0d\u5747\u5300\uff0c\u53d6\u51b3\u4e8e\u524d\u9762\u8bb2\u7684\u5bf9\u8c61\u7684 hashcode() \u65b9\u6cd5\u548c\u6270\u52a8\u51fd\u6570\uff09\u7684\u60c5\u51b5\u4e0b\uff0c\u65b0\u6570\u7ec4\u5143\u7d20\u4e5f\u4f1a\u88ab\u5206\u914d\u7684\u6bd4\u8f83\u5747\u5300\uff0c\u6700\u597d\u7684\u60c5\u51b5\u662f\u4f1a\u6709\u4e00\u534a\u5728\u65b0\u6570\u7ec4\u7684\u524d\u534a\u90e8\u5206\uff0c\u4e00\u534a\u5728\u65b0\u6570\u7ec4\u540e\u534a\u90e8\u5206\u3002<br \/>\n\u8fd9\u6837\u4e5f\u4f7f\u5f97\u6269\u5bb9\u673a\u5236\u53d8\u5f97\u7b80\u5355\u548c\u9ad8\u6548\uff0c\u6269\u5bb9\u540e\u53ea\u9700\u68c0\u67e5\u54c8\u5e0c\u503c\u9ad8\u4f4d\u7684\u53d8\u5316\u6765\u51b3\u5b9a\u5143\u7d20\u7684\u65b0\u4f4d\u7f6e\uff0c\u8981\u4e48\u4f4d\u7f6e\u4e0d\u53d8\uff08\u9ad8\u4f4d\u4e3a 0\uff09\uff0c\u8981\u4e48\u5c31\u662f\u79fb\u52a8\u5230\u65b0\u4f4d\u7f6e\uff08\u9ad8\u4f4d\u4e3a 1\uff0c\u539f\u7d22\u5f15\u4f4d\u7f6e+\u539f\u5bb9\u91cf\uff09\u3002<br \/>\n<strong>\u6700\u540e\uff0c\u7b80\u5355\u603b\u7ed3\u4e00\u4e0b HashMap \u7684\u957f\u5ea6\u662f 2 \u7684\u5e42\u6b21\u65b9\u7684\u539f\u56e0\uff1a<\/strong><br \/>\n1\u3001<strong>\u4f4d\u8fd0\u7b97\u6548\u7387\u66f4\u9ad8<\/strong>\uff1a\u4f4d\u8fd0\u7b97(&amp;)\u6bd4\u53d6\u4f59\u8fd0\u7b97(%)\u66f4\u9ad8\u6548\u3002\u5f53\u957f\u5ea6\u4e3a 2 \u7684\u5e42\u6b21\u65b9\u65f6\uff0chash % length \u7b49\u4ef7\u4e8e hash &amp; (length - 1)\u3002<br \/>\n2\u3001<strong>\u53ef\u4ee5\u66f4\u597d\u5730\u4fdd\u8bc1\u54c8\u5e0c\u503c\u7684\u5747\u5300\u5206\u5e03<\/strong>\uff1a\u6269\u5bb9\u4e4b\u540e\uff0c\u5728\u65e7\u6570\u7ec4\u5143\u7d20 hash \u503c\u6bd4\u8f83\u5747\u5300\u7684\u60c5\u51b5\u4e0b\uff0c\u65b0\u6570\u7ec4\u5143\u7d20\u4e5f\u4f1a\u88ab\u5206\u914d\u7684\u6bd4\u8f83\u5747\u5300\uff0c\u6700\u597d\u7684\u60c5\u51b5\u662f\u4f1a\u6709\u4e00\u534a\u5728\u65b0\u6570\u7ec4\u7684\u524d\u534a\u90e8\u5206\uff0c\u4e00\u534a\u5728\u65b0\u6570\u7ec4\u540e\u534a\u90e8\u5206\u3002<br \/>\n3\u3001<strong>\u6269\u5bb9\u673a\u5236\u53d8\u5f97\u7b80\u5355\u548c\u9ad8\u6548<\/strong>\uff1a\u6269\u5bb9\u540e\u53ea\u9700\u68c0\u67e5\u54c8\u5e0c\u503c\u9ad8\u4f4d\u7684\u53d8\u5316\u6765\u51b3\u5b9a\u5143\u7d20\u7684\u65b0\u4f4d\u7f6e\uff0c\u8981\u4e48\u4f4d\u7f6e\u4e0d\u53d8\uff08\u9ad8\u4f4d\u4e3a 0\uff09\uff0c\u8981\u4e48\u5c31\u662f\u79fb\u52a8\u5230\u65b0\u4f4d\u7f6e\uff08\u9ad8\u4f4d\u4e3a 1\uff0c\u539f\u7d22\u5f15\u4f4d\u7f6e+\u539f\u5bb9\u91cf\uff09\u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"HashMap_%E5%A4%9A%E7%BA%BF%E7%A8%8B%E6%93%8D%E4%BD%9C%E5%AF%BC%E8%87%B4%E6%AD%BB%E5%BE%AA%E7%8E%AF%E9%97%AE%E9%A2%98\"><\/span>HashMap \u591a\u7ebf\u7a0b\u64cd\u4f5c\u5bfc\u81f4\u6b7b\u5faa\u73af\u95ee\u9898<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>JDK1.7 \u53ca\u4e4b\u524d\u7248\u672c\u7684 HashMap \u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\u6269\u5bb9\u64cd\u4f5c\u53ef\u80fd\u5b58\u5728\u6b7b\u5faa\u73af\u95ee\u9898\uff0c\u8fd9\u662f\u7531\u4e8e\u5f53\u4e00\u4e2a\u6876\u4f4d\u4e2d\u6709\u591a\u4e2a\u5143\u7d20\u9700\u8981\u8fdb\u884c\u6269\u5bb9\u65f6\uff0c\u591a\u4e2a\u7ebf\u7a0b\u540c\u65f6\u5bf9\u94fe\u8868\u8fdb\u884c\u64cd\u4f5c\uff0c\u5934\u63d2\u6cd5\u53ef\u80fd\u4f1a\u5bfc\u81f4\u94fe\u8868\u4e2d\u7684\u8282\u70b9\u6307\u5411\u9519\u8bef\u7684\u4f4d\u7f6e\uff0c\u4ece\u800c\u5f62\u6210\u4e00\u4e2a\u73af\u5f62\u94fe\u8868\uff0c\u8fdb\u800c\u4f7f\u5f97\u67e5\u8be2\u5143\u7d20\u7684\u64cd\u4f5c\u9677\u5165\u6b7b\u5faa\u73af\u65e0\u6cd5\u7ed3\u675f\u3002<br \/>\n\u4e3a\u4e86\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\uff0cJDK1.8 \u7248\u672c\u7684 HashMap \u91c7\u7528\u4e86\u5c3e\u63d2\u6cd5\u800c\u4e0d\u662f\u5934\u63d2\u6cd5\u6765\u907f\u514d\u94fe\u8868\u5012\u7f6e\uff0c\u4f7f\u5f97\u63d2\u5165\u7684\u8282\u70b9\u6c38\u8fdc\u90fd\u662f\u653e\u5728\u94fe\u8868\u7684\u672b\u5c3e\uff0c\u907f\u514d\u4e86\u94fe\u8868\u4e2d\u7684\u73af\u5f62\u7ed3\u6784\u3002\u4f46\u662f\u8fd8\u662f\u4e0d\u5efa\u8bae\u5728\u591a\u7ebf\u7a0b\u4e0b\u4f7f\u7528 HashMap\uff0c\u56e0\u4e3a\u591a\u7ebf\u7a0b\u4e0b\u4f7f\u7528 HashMap \u8fd8\u662f\u4f1a\u5b58\u5728\u6570\u636e\u8986\u76d6\u7684\u95ee\u9898\u3002\u5e76\u53d1\u73af\u5883\u4e0b\uff0c\u63a8\u8350\u4f7f\u7528 ConcurrentHashMap \u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"HashMap_%E4%B8%BA%E4%BB%80%E4%B9%88%E7%BA%BF%E7%A8%8B%E4%B8%8D%E5%AE%89%E5%85%A8%EF%BC%9F\"><\/span>HashMap \u4e3a\u4ec0\u4e48\u7ebf\u7a0b\u4e0d\u5b89\u5168\uff1f<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>JDK1.7 \u53ca\u4e4b\u524d\u7248\u672c\uff0c\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\uff0cHashMap \u6269\u5bb9\u65f6\u4f1a\u9020\u6210\u6b7b\u5faa\u73af\u548c\u6570\u636e\u4e22\u5931\u7684\u95ee\u9898\u3002<br \/>\n\u6570\u636e\u4e22\u5931\u8fd9\u4e2a\u5728 JDK1.7 \u548c JDK 1.8 \u4e2d\u90fd\u5b58\u5728\uff0c\u8fd9\u91cc\u4ee5 JDK 1.8 \u4e3a\u4f8b\u8fdb\u884c\u4ecb\u7ecd\u3002<br \/>\nJDK 1.8 \u540e\uff0c\u5728 HashMap \u4e2d\uff0c\u591a\u4e2a\u952e\u503c\u5bf9\u53ef\u80fd\u4f1a\u88ab\u5206\u914d\u5230\u540c\u4e00\u4e2a\u6876\uff08bucket\uff09\uff0c\u5e76\u4ee5\u94fe\u8868\u6216\u7ea2\u9ed1\u6811\u7684\u5f62\u5f0f\u5b58\u50a8\u3002\u591a\u4e2a\u7ebf\u7a0b\u5bf9 HashMap \u7684 put \u64cd\u4f5c\u4f1a\u5bfc\u81f4\u7ebf\u7a0b\u4e0d\u5b89\u5168\uff0c\u5177\u4f53\u6765\u8bf4\u4f1a\u6709\u6570\u636e\u8986\u76d6\u7684\u98ce\u9669\u3002<br \/>\n<strong>\u4e3e\u4e2a\u4f8b\u5b50\uff1a<\/strong><br \/>\n\u4e24\u4e2a\u7ebf\u7a0b 1,2 \u540c\u65f6\u8fdb\u884c put \u64cd\u4f5c\uff0c\u5e76\u4e14\u53d1\u751f\u4e86\u54c8\u5e0c\u51b2\u7a81\uff08hash \u51fd\u6570\u8ba1\u7b97\u51fa\u7684\u63d2\u5165\u4e0b\u6807\u662f\u76f8\u540c\u7684\uff09\u3002\u4e0d\u540c\u7684\u7ebf\u7a0b\u53ef\u80fd\u5728\u4e0d\u540c\u7684\u65f6\u95f4\u7247\u83b7\u5f97 CPU \u6267\u884c\u7684\u673a\u4f1a\uff0c\u5f53\u524d\u7ebf\u7a0b 1 \u6267\u884c\u5b8c\u54c8\u5e0c\u51b2\u7a81\u5224\u65ad\u540e\uff0c\u7531\u4e8e\u65f6\u95f4\u7247\u8017\u5c3d\u6302\u8d77\u3002\u7ebf\u7a0b 2 \u5148\u5b8c\u6210\u4e86\u63d2\u5165\u64cd\u4f5c\u3002\u968f\u540e\uff0c\u7ebf\u7a0b 1 \u83b7\u5f97\u65f6\u95f4\u7247\uff0c\u7531\u4e8e\u4e4b\u524d\u5df2\u7ecf\u8fdb\u884c\u8fc7 hash \u78b0\u649e\u7684\u5224\u65ad\uff0c\u6240\u6709\u6b64\u65f6\u4f1a\u76f4\u63a5\u8fdb\u884c\u63d2\u5165\uff0c\u8fd9\u5c31\u5bfc\u81f4\u7ebf\u7a0b 2 \u63d2\u5165\u7684\u6570\u636e\u88ab\u7ebf\u7a0b 1 \u8986\u76d6\u4e86\u3002<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">public V put(K key, V value) {\n    return putVal(hash(key), key, value, false, true);\n}\n\nfinal V putVal(int hash, K key, V value, boolean onlyIfAbsent,\n                   boolean evict) {\n    \/\/ ...\n    \/\/ \u5224\u65ad\u662f\u5426\u51fa\u73b0 hash \u78b0\u649e\n    \/\/ (n - 1) &amp; hash \u786e\u5b9a\u5143\u7d20\u5b58\u653e\u5728\u54ea\u4e2a\u6876\u4e2d\uff0c\u6876\u4e3a\u7a7a\uff0c\u65b0\u751f\u6210\u7ed3\u70b9\u653e\u5165\u6876\u4e2d(\u6b64\u65f6\uff0c\u8fd9\u4e2a\u7ed3\u70b9\u662f\u653e\u5728\u6570\u7ec4\u4e2d)\n    if ((p = tab[i = (n - 1) &amp; hash]) == null)\n        tab[i] = newNode(hash, key, value, null);\n    \/\/ \u6876\u4e2d\u5df2\u7ecf\u5b58\u5728\u5143\u7d20\uff08\u5904\u7406hash\u51b2\u7a81\uff09\n    else {\n    \/\/ ...\n}<\/code><\/pre>\n<p><strong>\u8fd8\u6709\u4e00\u79cd\u60c5\u51b5\u662f\u8fd9\u4e24\u4e2a\u7ebf\u7a0b\u540c\u65f6 put \u64cd\u4f5c\u5bfc\u81f4 size \u7684\u503c\u4e0d\u6b63\u786e\uff0c\u8fdb\u800c\u5bfc\u81f4\u6570\u636e\u8986\u76d6\u7684\u95ee\u9898\uff1a<\/strong><br \/>\n1\u3001\u7ebf\u7a0b 1 \u6267\u884c if(++size &gt; threshold) \u5224\u65ad\u65f6\uff0c\u5047\u8bbe\u83b7\u5f97 size \u7684\u503c\u4e3a 10\uff0c\u7531\u4e8e\u65f6\u95f4\u7247\u8017\u5c3d\u6302\u8d77\u3002<br \/>\n2\u3001\u7ebf\u7a0b 2 \u4e5f\u6267\u884c if(++size &gt; threshold) \u5224\u65ad\uff0c\u83b7\u5f97 size \u7684\u503c\u4e5f\u4e3a 10\uff0c\u5e76\u5c06\u5143\u7d20\u63d2\u5165\u5230\u8be5\u6876\u4f4d\u4e2d\uff0c\u5e76\u5c06 size \u7684\u503c\u66f4\u65b0\u4e3a 11\u3002<br \/>\n3\u3001\u968f\u540e\uff0c\u7ebf\u7a0b 1 \u83b7\u5f97\u65f6\u95f4\u7247\uff0c\u5b83\u4e5f\u5c06\u5143\u7d20\u653e\u5165\u6876\u4f4d\u4e2d\uff0c\u5e76\u5c06 size \u7684\u503c\u66f4\u65b0\u4e3a 11\u3002<br \/>\n4\u3001\u7ebf\u7a0b 1\u30012 \u90fd\u6267\u884c\u4e86\u4e00\u6b21 put \u64cd\u4f5c\uff0c\u4f46\u662f size \u7684\u503c\u53ea\u589e\u52a0\u4e86 1\uff0c\u4e5f\u5c31\u5bfc\u81f4\u5b9e\u9645\u4e0a\u53ea\u6709\u4e00\u4e2a\u5143\u7d20\u88ab\u6dfb\u52a0\u5230\u4e86 HashMap \u4e2d\u3002<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">public V put(K key, V value) {\n    return putVal(hash(key), key, value, false, true);\n}\n\nfinal V putVal(int hash, K key, V value, boolean onlyIfAbsent,\n                   boolean evict) {\n    \/\/ ...\n    \/\/ \u5b9e\u9645\u5927\u5c0f\u5927\u4e8e\u9608\u503c\u5219\u6269\u5bb9\n    if (++size &gt; threshold)\n        resize();\n    \/\/ \u63d2\u5165\u540e\u56de\u8c03\n    afterNodeInsertion(evict);\n    return null;\n}<\/code><\/pre>\n<h3><span class=\"ez-toc-section\" id=\"ConcurrentHashMap_%E5%92%8C_Hashtable_%E7%9A%84%E5%8C%BA%E5%88%AB\"><\/span>ConcurrentHashMap \u548c Hashtable \u7684\u533a\u522b<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>ConcurrentHashMap \u548c Hashtable \u7684\u533a\u522b\u4e3b\u8981\u4f53\u73b0\u5728\u5b9e\u73b0\u7ebf\u7a0b\u5b89\u5168\u7684\u65b9\u5f0f\u4e0a\u4e0d\u540c\u3002<\/p>\n<p><strong>\u5e95\u5c42\u6570\u636e\u7ed3\u6784\uff1a<\/strong> JDK1.7 \u7684 ConcurrentHashMap \u5e95\u5c42\u91c7\u7528 \u5206\u6bb5\u7684\u6570\u7ec4+\u94fe\u8868 \u5b9e\u73b0\uff0c\u5728 JDK1.8 \u4e2d\u91c7\u7528\u7684\u6570\u636e\u7ed3\u6784\u8ddf HashMap \u7684\u7ed3\u6784\u4e00\u6837\uff0c\u6570\u7ec4+\u94fe\u8868\/\u7ea2\u9ed1\u4e8c\u53c9\u6811\u3002Hashtable \u548c JDK1.8 \u4e4b\u524d\u7684 HashMap \u7684\u5e95\u5c42\u6570\u636e\u7ed3\u6784\u7c7b\u4f3c\u90fd\u662f\u91c7\u7528 \u6570\u7ec4+\u94fe\u8868 \u7684\u5f62\u5f0f\uff0c\u6570\u7ec4\u662f HashMap \u7684\u4e3b\u4f53\uff0c\u94fe\u8868\u5219\u662f\u4e3b\u8981\u4e3a\u4e86\u89e3\u51b3\u54c8\u5e0c\u51b2\u7a81\u800c\u5b58\u5728\u7684\uff1b<\/p>\n<p><strong>\u5b9e\u73b0\u7ebf\u7a0b\u5b89\u5168\u7684\u65b9\u5f0f\uff08\u91cd\u8981\uff09\uff1a<\/strong><br \/>\n\u5728 JDK1.7 \u7684\u65f6\u5019\uff0cConcurrentHashMap \u5bf9\u6574\u4e2a\u6876\u6570\u7ec4\u8fdb\u884c\u4e86\u5206\u5272\u5206\u6bb5(Segment\uff0c\u5206\u6bb5\u9501)\uff0c\u6bcf\u4e00\u628a\u9501\u53ea\u9501\u5bb9\u5668\u5176\u4e2d\u4e00\u90e8\u5206\u6570\u636e\uff08\u4e0b\u9762\u6709\u793a\u610f\u56fe\uff09\uff0c\u591a\u7ebf\u7a0b\u8bbf\u95ee\u5bb9\u5668\u91cc\u4e0d\u540c\u6570\u636e\u6bb5\u7684\u6570\u636e\uff0c\u5c31\u4e0d\u4f1a\u5b58\u5728\u9501\u7ade\u4e89\uff0c\u63d0\u9ad8\u5e76\u53d1\u8bbf\u95ee\u7387\u3002\u5230\u4e86 JDK1.8 \u7684\u65f6\u5019\uff0cConcurrentHashMap \u5df2\u7ecf\u6452\u5f03\u4e86 Segment \u7684\u6982\u5ff5\uff0c\u800c\u662f\u76f4\u63a5\u7528 Node \u6570\u7ec4+\u94fe\u8868+\u7ea2\u9ed1\u6811\u7684\u6570\u636e\u7ed3\u6784\u6765\u5b9e\u73b0\uff0c\u5e76\u53d1\u63a7\u5236\u4f7f\u7528 synchronized \u548c CAS \u6765\u64cd\u4f5c\u3002\uff08JDK1.6 \u4ee5\u540e synchronized \u9501\u505a\u4e86\u5f88\u591a\u4f18\u5316\uff09 \u6574\u4e2a\u770b\u8d77\u6765\u5c31\u50cf\u662f\u4f18\u5316\u8fc7\u4e14\u7ebf\u7a0b\u5b89\u5168\u7684 HashMap\uff0c\u867d\u7136\u5728 JDK1.8 \u4e2d\u8fd8\u80fd\u770b\u5230 Segment \u7684\u6570\u636e\u7ed3\u6784\uff0c\u4f46\u662f\u5df2\u7ecf\u7b80\u5316\u4e86\u5c5e\u6027\uff0c\u53ea\u662f\u4e3a\u4e86\u517c\u5bb9\u65e7\u7248\u672c\uff1b<br \/>\n<strong>Hashtable(\u540c\u4e00\u628a\u9501)<\/strong> :\u4f7f\u7528 synchronized \u6765\u4fdd\u8bc1\u7ebf\u7a0b\u5b89\u5168\uff0c\u6548\u7387\u975e\u5e38\u4f4e\u4e0b\u3002\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u8bbf\u95ee\u540c\u6b65\u65b9\u6cd5\u65f6\uff0c\u5176\u4ed6\u7ebf\u7a0b\u4e5f\u8bbf\u95ee\u540c\u6b65\u65b9\u6cd5\uff0c\u53ef\u80fd\u4f1a\u8fdb\u5165\u963b\u585e\u6216\u8f6e\u8be2\u72b6\u6001\uff0c\u5982\u4f7f\u7528 put \u6dfb\u52a0\u5143\u7d20\uff0c\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u4e0d\u80fd\u4f7f\u7528 put \u6dfb\u52a0\u5143\u7d20\uff0c\u4e5f\u4e0d\u80fd\u4f7f\u7528 get\uff0c\u7ade\u4e89\u4f1a\u8d8a\u6765\u8d8a\u6fc0\u70c8\u6548\u7387\u8d8a\u4f4e\u3002<\/p>\n<p>\u4e0b\u9762\uff0c\u6211\u4eec\u518d\u6765\u770b\u770b\u4e24\u8005\u5e95\u5c42\u6570\u636e\u7ed3\u6784\u7684\u5bf9\u6bd4\u56fe\u3002<br \/>\n<img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752389424251.png\" alt=\"file\" \/><\/p>\n<p><img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752389431348.png\" alt=\"file\" \/><\/p>\n<p>ConcurrentHashMap \u662f\u7531 Segment \u6570\u7ec4\u7ed3\u6784\u548c HashEntry \u6570\u7ec4\u7ed3\u6784\u7ec4\u6210\u3002Segment \u6570\u7ec4\u4e2d\u7684\u6bcf\u4e2a\u5143\u7d20\u5305\u542b\u4e00\u4e2a HashEntry \u6570\u7ec4\uff0c\u6bcf\u4e2a HashEntry \u6570\u7ec4\u5c5e\u4e8e\u94fe\u8868\u7ed3\u6784\u3002<br \/>\n<img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752389463723.png\" alt=\"file\" \/><br \/>\nJDK1.8 \u7684 ConcurrentHashMap \u4e0d\u518d\u662f Segment \u6570\u7ec4 + HashEntry \u6570\u7ec4 + \u94fe\u8868\uff0c\u800c\u662f Node \u6570\u7ec4 + \u94fe\u8868 \/ \u7ea2\u9ed1\u6811\u3002\u4e0d\u8fc7\uff0cNode \u53ea\u80fd\u7528\u4e8e\u94fe\u8868\u7684\u60c5\u51b5\uff0c\u7ea2\u9ed1\u6811\u7684\u60c5\u51b5\u9700\u8981\u4f7f\u7528 TreeNode\u3002\u5f53\u51b2\u7a81\u94fe\u8868\u8fbe\u5230\u4e00\u5b9a\u957f\u5ea6\u65f6\uff0c\u94fe\u8868\u4f1a\u8f6c\u6362\u6210\u7ea2\u9ed1\u6811\u3002<\/p>\n<p>TreeNode\u662f\u5b58\u50a8\u7ea2\u9ed1\u6811\u8282\u70b9\uff0c\u88abTreeBin\u5305\u88c5\u3002TreeBin\u901a\u8fc7root\u5c5e\u6027\u7ef4\u62a4\u7ea2\u9ed1\u6811\u7684\u6839\u7ed3\u70b9\uff0c\u56e0\u4e3a\u7ea2\u9ed1\u6811\u5728\u65cb\u8f6c\u7684\u65f6\u5019\uff0c\u6839\u7ed3\u70b9\u53ef\u80fd\u4f1a\u88ab\u5b83\u539f\u6765\u7684\u5b50\u8282\u70b9\u66ff\u6362\u6389\uff0c\u5728\u8fd9\u4e2a\u65f6\u95f4\u70b9\uff0c\u5982\u679c\u6709\u5176\u4ed6\u7ebf\u7a0b\u8981\u5199\u8fd9\u68f5\u7ea2\u9ed1\u6811\u5c31\u4f1a\u53d1\u751f\u7ebf\u7a0b\u4e0d\u5b89\u5168\u95ee\u9898\uff0c\u6240\u4ee5\u5728 ConcurrentHashMap \u4e2dTreeBin\u901a\u8fc7waiter\u5c5e\u6027\u7ef4\u62a4\u5f53\u524d\u4f7f\u7528\u8fd9\u68f5\u7ea2\u9ed1\u6811\u7684\u7ebf\u7a0b\uff0c\u6765\u9632\u6b62\u5176\u4ed6\u7ebf\u7a0b\u7684\u8fdb\u5165\u3002<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">static final class TreeBin&lt;K,V&gt; extends Node&lt;K,V&gt; {\n        TreeNode&lt;K,V&gt; root;\n        volatile TreeNode&lt;K,V&gt; first;\n        volatile Thread waiter;\n        volatile int lockState;\n        \/\/ values for lockState\n        static final int WRITER = 1; \/\/ set while holding write lock\n        static final int WAITER = 2; \/\/ set when waiting for write lock\n        static final int READER = 4; \/\/ increment value for setting read lock\n...\n}<\/code><\/pre>\n<h3><span class=\"ez-toc-section\" id=\"ConcurrentHashMap_%E7%BA%BF%E7%A8%8B%E5%AE%89%E5%85%A8%E7%9A%84%E5%85%B7%E4%BD%93%E5%AE%9E%E7%8E%B0%E6%96%B9%E5%BC%8F%E5%BA%95%E5%B1%82%E5%85%B7%E4%BD%93%E5%AE%9E%E7%8E%B0\"><\/span>ConcurrentHashMap \u7ebf\u7a0b\u5b89\u5168\u7684\u5177\u4f53\u5b9e\u73b0\u65b9\u5f0f\/\u5e95\u5c42\u5177\u4f53\u5b9e\u73b0<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752389530506.png\" alt=\"file\" \/><\/p>\n<p>\u9996\u5148\u5c06\u6570\u636e\u5206\u4e3a\u4e00\u6bb5\u4e00\u6bb5\uff08\u8fd9\u4e2a\u201c\u6bb5\u201d\u5c31\u662f Segment\uff09\u7684\u5b58\u50a8\uff0c\u7136\u540e\u7ed9\u6bcf\u4e00\u6bb5\u6570\u636e\u914d\u4e00\u628a\u9501\uff0c\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u5360\u7528\u9501\u8bbf\u95ee\u5176\u4e2d\u4e00\u4e2a\u6bb5\u6570\u636e\u65f6\uff0c\u5176\u4ed6\u6bb5\u7684\u6570\u636e\u4e5f\u80fd\u88ab\u5176\u4ed6\u7ebf\u7a0b\u8bbf\u95ee\u3002<br \/>\n<strong>ConcurrentHashMap \u662f\u7531 Segment \u6570\u7ec4\u7ed3\u6784\u548c HashEntry \u6570\u7ec4\u7ed3\u6784\u7ec4\u6210\u3002<\/strong><\/p>\n<p>Segment \u7ee7\u627f\u4e86 ReentrantLock,\u6240\u4ee5 Segment \u662f\u4e00\u79cd\u53ef\u91cd\u5165\u9501\uff0c\u626e\u6f14\u9501\u7684\u89d2\u8272\u3002HashEntry \u7528\u4e8e\u5b58\u50a8\u952e\u503c\u5bf9\u6570\u636e\u3002<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">static class Segment&lt;K,V&gt; extends ReentrantLock implements Serializable {\n}<\/code><\/pre>\n<p>\u4e00\u4e2a ConcurrentHashMap \u91cc\u5305\u542b\u4e00\u4e2a Segment \u6570\u7ec4\uff0cSegment \u7684\u4e2a\u6570\u4e00\u65e6<strong>\u521d\u59cb\u5316\u5c31\u4e0d\u80fd\u6539\u53d8<\/strong>\u3002 Segment \u6570\u7ec4\u7684\u5927\u5c0f\u9ed8\u8ba4\u662f 16\uff0c\u4e5f\u5c31\u662f\u8bf4\u9ed8\u8ba4\u53ef\u4ee5\u540c\u65f6\u652f\u6301 16 \u4e2a\u7ebf\u7a0b\u5e76\u53d1\u5199\u3002<\/p>\n<p>Segment \u7684\u7ed3\u6784\u548c HashMap \u7c7b\u4f3c\uff0c\u662f\u4e00\u79cd\u6570\u7ec4\u548c\u94fe\u8868\u7ed3\u6784\uff0c\u4e00\u4e2a Segment \u5305\u542b\u4e00\u4e2a HashEntry \u6570\u7ec4\uff0c\u6bcf\u4e2a HashEntry \u662f\u4e00\u4e2a\u94fe\u8868\u7ed3\u6784\u7684\u5143\u7d20\uff0c\u6bcf\u4e2a Segment \u5b88\u62a4\u7740\u4e00\u4e2a HashEntry \u6570\u7ec4\u91cc\u7684\u5143\u7d20\uff0c\u5f53\u5bf9 HashEntry \u6570\u7ec4\u7684\u6570\u636e\u8fdb\u884c\u4fee\u6539\u65f6\uff0c\u5fc5\u987b\u9996\u5148\u83b7\u5f97\u5bf9\u5e94\u7684 Segment \u7684\u9501\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5bf9\u540c\u4e00 Segment \u7684\u5e76\u53d1\u5199\u5165\u4f1a\u88ab\u963b\u585e\uff0c\u4e0d\u540c Segment \u7684\u5199\u5165\u662f\u53ef\u4ee5\u5e76\u53d1\u6267\u884c\u7684\u3002<br \/>\n<img decoding=\"async\" src=\"https:\/\/yingjun.run\/wp-content\/uploads\/2025\/07\/image-1752389633768.png\" alt=\"file\" \/><\/p>\n<p>Java 8 \u51e0\u4e4e\u5b8c\u5168\u91cd\u5199\u4e86 ConcurrentHashMap\uff0c\u4ee3\u7801\u91cf\u4ece\u539f\u6765 Java 7 \u4e2d\u7684 1000 \u591a\u884c\uff0c\u53d8\u6210\u4e86\u73b0\u5728\u7684 6000 \u591a\u884c\u3002<\/p>\n<p>ConcurrentHashMap \u53d6\u6d88\u4e86 Segment \u5206\u6bb5\u9501\uff0c\u91c7\u7528 Node + CAS + synchronized \u6765\u4fdd\u8bc1\u5e76\u53d1\u5b89\u5168\u3002\u6570\u636e\u7ed3\u6784\u8ddf HashMap 1.8 \u7684\u7ed3\u6784\u7c7b\u4f3c\uff0c\u6570\u7ec4+\u94fe\u8868\/\u7ea2\u9ed1\u4e8c\u53c9\u6811\u3002Java 8 \u5728\u94fe\u8868\u957f\u5ea6\u8d85\u8fc7\u4e00\u5b9a\u9608\u503c\uff088\uff09\u65f6\u5c06\u94fe\u8868\uff08\u5bfb\u5740\u65f6\u95f4\u590d\u6742\u5ea6\u4e3a O(N)\uff09\u8f6c\u6362\u4e3a\u7ea2\u9ed1\u6811\uff08\u5bfb\u5740\u65f6\u95f4\u590d\u6742\u5ea6\u4e3a O(log(N))\uff09\u3002<\/p>\n<p>Java 8 \u4e2d\uff0c\u9501\u7c92\u5ea6\u66f4\u7ec6\uff0csynchronized \u53ea\u9501\u5b9a\u5f53\u524d\u94fe\u8868\u6216\u7ea2\u9ed1\u4e8c\u53c9\u6811\u7684\u9996\u8282\u70b9\uff0c\u8fd9\u6837\u53ea\u8981 hash \u4e0d\u51b2\u7a81\uff0c\u5c31\u4e0d\u4f1a\u4ea7\u751f\u5e76\u53d1\uff0c\u5c31\u4e0d\u4f1a\u5f71\u54cd\u5176\u4ed6 Node \u7684\u8bfb\u5199\uff0c\u6548\u7387\u5927\u5e45\u63d0\u5347\u3002<\/p>\n<h3><span class=\"ez-toc-section\" id=\"JDK_17_%E5%92%8C_JDK_18_%E7%9A%84_ConcurrentHashMap_%E5%AE%9E%E7%8E%B0%E6%9C%89%E4%BB%80%E4%B9%88%E4%B8%8D%E5%90%8C%EF%BC%9F\"><\/span>JDK 1.7 \u548c JDK 1.8 \u7684 ConcurrentHashMap \u5b9e\u73b0\u6709\u4ec0\u4e48\u4e0d\u540c\uff1f<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><strong>\u7ebf\u7a0b\u5b89\u5168\u5b9e\u73b0\u65b9\u5f0f<\/strong>\uff1aJDK 1.7 \u91c7\u7528 Segment \u5206\u6bb5\u9501\u6765\u4fdd\u8bc1\u5b89\u5168\uff0c Segment \u662f\u7ee7\u627f\u81ea ReentrantLock\u3002JDK1.8 \u653e\u5f03\u4e86 Segment \u5206\u6bb5\u9501\u7684\u8bbe\u8ba1\uff0c\u91c7\u7528 Node + CAS + synchronized \u4fdd\u8bc1\u7ebf\u7a0b\u5b89\u5168\uff0c\u9501\u7c92\u5ea6\u66f4\u7ec6\uff0csynchronized \u53ea\u9501\u5b9a\u5f53\u524d\u94fe\u8868\u6216\u7ea2\u9ed1\u4e8c\u53c9\u6811\u7684\u9996\u8282\u70b9\u3002<br \/>\n<strong>Hash \u78b0\u649e\u89e3\u51b3\u65b9\u6cd5 <\/strong>: JDK 1.7 \u91c7\u7528\u62c9\u94fe\u6cd5\uff0cJDK1.8 \u91c7\u7528\u62c9\u94fe\u6cd5\u7ed3\u5408\u7ea2\u9ed1\u6811\uff08\u94fe\u8868\u957f\u5ea6\u8d85\u8fc7\u4e00\u5b9a\u9608\u503c\u65f6\uff0c\u5c06\u94fe\u8868\u8f6c\u6362\u4e3a\u7ea2\u9ed1\u6811\uff09\u3002<br \/>\n<strong>\u5e76\u53d1\u5ea6<\/strong>\uff1aJDK 1.7 \u6700\u5927\u5e76\u53d1\u5ea6\u662f Segment \u7684\u4e2a\u6570\uff0c\u9ed8\u8ba4\u662f 16\u3002JDK 1.8 \u6700\u5927\u5e76\u53d1\u5ea6\u662f Node \u6570\u7ec4\u7684\u5927\u5c0f\uff0c\u5e76\u53d1\u5ea6\u66f4\u5927<\/p>\n<h3><span class=\"ez-toc-section\" id=\"ConcurrentHashMap_%E4%B8%BA%E4%BB%80%E4%B9%88_key_%E5%92%8C_value_%E4%B8%8D%E8%83%BD%E4%B8%BA_null%EF%BC%9F\"><\/span>ConcurrentHashMap \u4e3a\u4ec0\u4e48 key \u548c value \u4e0d\u80fd\u4e3a null\uff1f<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>ConcurrentHashMap \u7684 key \u548c value \u4e0d\u80fd\u4e3a null \u4e3b\u8981\u662f\u4e3a\u4e86\u907f\u514d\u4e8c\u4e49\u6027\u3002null \u662f\u4e00\u4e2a\u7279\u6b8a\u7684\u503c\uff0c\u8868\u793a\u6ca1\u6709\u5bf9\u8c61\u6216\u6ca1\u6709\u5f15\u7528\u3002\u5982\u679c\u4f60\u7528 null \u4f5c\u4e3a\u952e\uff0c\u90a3\u4e48\u4f60\u5c31\u65e0\u6cd5\u533a\u5206\u8fd9\u4e2a\u952e\u662f\u5426\u5b58\u5728\u4e8e ConcurrentHashMap \u4e2d\uff0c\u8fd8\u662f\u6839\u672c\u6ca1\u6709\u8fd9\u4e2a\u952e\u3002\u540c\u6837\uff0c\u5982\u679c\u4f60\u7528 null \u4f5c\u4e3a\u503c\uff0c\u90a3\u4e48\u4f60\u5c31\u65e0\u6cd5\u533a\u5206\u8fd9\u4e2a\u503c\u662f\u5426\u662f\u771f\u6b63\u5b58\u50a8\u5728 ConcurrentHashMap \u4e2d\u7684\uff0c\u8fd8\u662f\u56e0\u4e3a\u627e\u4e0d\u5230\u5bf9\u5e94\u7684\u952e\u800c\u8fd4\u56de\u7684\u3002<\/p>\n<p>\u62ff get \u65b9\u6cd5\u53d6\u503c\u6765\u8bf4\uff0c\u8fd4\u56de\u7684\u7ed3\u679c\u4e3a null \u5b58\u5728\u4e24\u79cd\u60c5\u51b5\uff1a<br \/>\n\u503c\u6ca1\u6709\u5728\u96c6\u5408\u4e2d \uff1b<br \/>\n\u503c\u672c\u8eab\u5c31\u662f null\u3002<br \/>\n\u8fd9\u4e5f\u5c31\u662f\u4e8c\u4e49\u6027\u7684\u7531\u6765\u3002<\/p>\n<p>\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\uff0c\u5b58\u5728\u4e00\u4e2a\u7ebf\u7a0b\u64cd\u4f5c\u8be5 ConcurrentHashMap \u65f6\uff0c\u5176\u4ed6\u7684\u7ebf\u7a0b\u5c06\u8be5 ConcurrentHashMap \u4fee\u6539\u7684\u60c5\u51b5\uff0c\u6240\u4ee5\u65e0\u6cd5\u901a\u8fc7 containsKey(key) \u6765\u5224\u65ad\u5426\u5b58\u5728\u8fd9\u4e2a\u952e\u503c\u5bf9\uff0c\u4e5f\u5c31\u6ca1\u529e\u6cd5\u89e3\u51b3\u4e8c\u4e49\u6027\u95ee\u9898\u4e86\u3002<\/p>\n<p>\u4e0e\u6b64\u5f62\u6210\u5bf9\u6bd4\u7684\u662f\uff0cHashMap \u53ef\u4ee5\u5b58\u50a8 null \u7684 key \u548c value\uff0c\u4f46 null \u4f5c\u4e3a\u952e\u53ea\u80fd\u6709\u4e00\u4e2a\uff0cnull \u4f5c\u4e3a\u503c\u53ef\u4ee5\u6709\u591a\u4e2a\u3002\u5982\u679c\u4f20\u5165 null \u4f5c\u4e3a\u53c2\u6570\uff0c\u5c31\u4f1a\u8fd4\u56de hash \u503c\u4e3a 0 \u7684\u4f4d\u7f6e\u7684\u503c\u3002\u5355\u7ebf\u7a0b\u73af\u5883\u4e0b\uff0c\u4e0d\u5b58\u5728\u4e00\u4e2a\u7ebf\u7a0b\u64cd\u4f5c\u8be5 HashMap \u65f6\uff0c\u5176\u4ed6\u7684\u7ebf\u7a0b\u5c06\u8be5 HashMap \u4fee\u6539\u7684\u60c5\u51b5\uff0c\u6240\u4ee5\u53ef\u4ee5\u901a\u8fc7 contains(key)\u6765\u505a\u5224\u65ad\u662f\u5426\u5b58\u5728\u8fd9\u4e2a\u952e\u503c\u5bf9\uff0c\u4ece\u800c\u505a\u76f8\u5e94\u7684\u5904\u7406\uff0c\u4e5f\u5c31\u4e0d\u5b58\u5728\u4e8c\u4e49\u6027\u95ee\u9898\u3002<\/p>\n<p>\u4e5f\u5c31\u662f\u8bf4\uff0c\u591a\u7ebf\u7a0b\u4e0b\u65e0\u6cd5\u6b63\u786e\u5224\u5b9a\u952e\u503c\u5bf9\u662f\u5426\u5b58\u5728\uff08\u5b58\u5728\u5176\u4ed6\u7ebf\u7a0b\u4fee\u6539\u7684\u60c5\u51b5\uff09\uff0c\u5355\u7ebf\u7a0b\u662f\u53ef\u4ee5\u7684\uff08\u4e0d\u5b58\u5728\u5176\u4ed6\u7ebf\u7a0b\u4fee\u6539\u7684\u60c5\u51b5\uff09\u3002<br \/>\n\u5982\u679c\u4f60\u786e\u5b9e\u9700\u8981\u5728 ConcurrentHashMap \u4e2d\u4f7f\u7528 null \u7684\u8bdd\uff0c\u53ef\u4ee5\u4f7f\u7528\u4e00\u4e2a\u7279\u6b8a\u7684\u9759\u6001\u7a7a\u5bf9\u8c61\u6765\u4ee3\u66ff null\u3002<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">public static final Object NULL = new Object();<\/code><\/pre>\n<h3><span class=\"ez-toc-section\" id=\"ConcurrentHashMap_%E8%83%BD%E4%BF%9D%E8%AF%81%E5%A4%8D%E5%90%88%E6%93%8D%E4%BD%9C%E7%9A%84%E5%8E%9F%E5%AD%90%E6%80%A7%E5%90%97%EF%BC%9F\"><\/span>ConcurrentHashMap \u80fd\u4fdd\u8bc1\u590d\u5408\u64cd\u4f5c\u7684\u539f\u5b50\u6027\u5417\uff1f<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>ConcurrentHashMap \u662f\u7ebf\u7a0b\u5b89\u5168\u7684\uff0c\u610f\u5473\u7740\u5b83\u53ef\u4ee5\u4fdd\u8bc1\u591a\u4e2a\u7ebf\u7a0b\u540c\u65f6\u5bf9\u5b83\u8fdb\u884c\u8bfb\u5199\u64cd\u4f5c\u65f6\uff0c\u4e0d\u4f1a\u51fa\u73b0\u6570\u636e\u4e0d\u4e00\u81f4\u7684\u60c5\u51b5\uff0c\u4e5f\u4e0d\u4f1a\u5bfc\u81f4 JDK1.7 \u53ca\u4e4b\u524d\u7248\u672c\u7684 HashMap \u591a\u7ebf\u7a0b\u64cd\u4f5c\u5bfc\u81f4\u6b7b\u5faa\u73af\u95ee\u9898\u3002\u4f46\u662f\uff0c\u8fd9\u5e76\u4e0d\u610f\u5473\u7740\u5b83\u53ef\u4ee5\u4fdd\u8bc1\u6240\u6709\u7684\u590d\u5408\u64cd\u4f5c\u90fd\u662f\u539f\u5b50\u6027\u7684\uff0c\u4e00\u5b9a\u4e0d\u8981\u641e\u6df7\u4e86\uff01<\/p>\n<p>\u590d\u5408\u64cd\u4f5c\u662f\u6307\u7531\u591a\u4e2a\u57fa\u672c\u64cd\u4f5c(\u5982put\u3001get\u3001remove\u3001containsKey\u7b49)\u7ec4\u6210\u7684\u64cd\u4f5c\uff0c\u4f8b\u5982\u5148\u5224\u65ad\u67d0\u4e2a\u952e\u662f\u5426\u5b58\u5728containsKey(key)\uff0c\u7136\u540e\u6839\u636e\u7ed3\u679c\u8fdb\u884c\u63d2\u5165\u6216\u66f4\u65b0put(key, value)\u3002\u8fd9\u79cd\u64cd\u4f5c\u5728\u6267\u884c\u8fc7\u7a0b\u4e2d\u53ef\u80fd\u4f1a\u88ab\u5176\u4ed6\u7ebf\u7a0b\u6253\u65ad\uff0c\u5bfc\u81f4\u7ed3\u679c\u4e0d\u7b26\u5408\u9884\u671f\u3002<\/p>\n<p>\u4f8b\u5982\uff0c\u6709\u4e24\u4e2a\u7ebf\u7a0b A \u548c B \u540c\u65f6\u5bf9 ConcurrentHashMap \u8fdb\u884c\u590d\u5408\u64cd\u4f5c\uff0c\u5982\u4e0b\uff1a<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">\/\/ \u7ebf\u7a0b A\nif (!map.containsKey(key)) {\nmap.put(key, value);\n}\n\/\/ \u7ebf\u7a0b B\nif (!map.containsKey(key)) {\nmap.put(key, anotherValue);\n}<\/code><\/pre>\n<p>\u5982\u679c\u7ebf\u7a0b A \u548c B \u7684\u6267\u884c\u987a\u5e8f\u662f\u8fd9\u6837\uff1a<br \/>\n1\u3001\u7ebf\u7a0b A \u5224\u65ad map \u4e2d\u4e0d\u5b58\u5728 key<br \/>\n2\u3001\u7ebf\u7a0b B \u5224\u65ad map \u4e2d\u4e0d\u5b58\u5728 key<br \/>\n3\u3001\u7ebf\u7a0b B \u5c06 (key, anotherValue) \u63d2\u5165 map<br \/>\n4\u3001\u7ebf\u7a0b A \u5c06 (key, value) \u63d2\u5165 map<\/p>\n<p>\u90a3\u4e48\u6700\u7ec8\u7684\u7ed3\u679c\u662f (key, value)\uff0c\u800c\u4e0d\u662f\u9884\u671f\u7684 (key, anotherValue)\u3002\u8fd9\u5c31\u662f\u590d\u5408\u64cd\u4f5c\u7684\u975e\u539f\u5b50\u6027\u5bfc\u81f4\u7684\u95ee\u9898\u3002<\/p>\n<p><strong>\u90a3\u5982\u4f55\u4fdd\u8bc1 ConcurrentHashMap \u590d\u5408\u64cd\u4f5c\u7684\u539f\u5b50\u6027\u5462\uff1f<\/strong><\/p>\n<p>ConcurrentHashMap \u63d0\u4f9b\u4e86\u4e00\u4e9b\u539f\u5b50\u6027\u7684\u590d\u5408\u64cd\u4f5c\uff0c\u5982 putIfAbsent\u3001compute\u3001computeIfAbsent \u3001computeIfPresent\u3001merge\u7b49\u3002\u8fd9\u4e9b\u65b9\u6cd5\u90fd\u53ef\u4ee5\u63a5\u53d7\u4e00\u4e2a\u51fd\u6570\u4f5c\u4e3a\u53c2\u6570\uff0c\u6839\u636e\u7ed9\u5b9a\u7684 key \u548c value \u6765\u8ba1\u7b97\u4e00\u4e2a\u65b0\u7684 value\uff0c\u5e76\u4e14\u5c06\u5176\u66f4\u65b0\u5230 map \u4e2d\u3002<\/p>\n<p>\u4e0a\u9762\u7684\u4ee3\u7801\u53ef\u4ee5\u6539\u5199\u4e3a\uff1a<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">\/\/ \u7ebf\u7a0b A\nmap.putIfAbsent(key, value);\n\/\/ \u7ebf\u7a0b B\nmap.putIfAbsent(key, anotherValue);<\/code><\/pre>\n<p>\u6216\u8005\uff1a<\/p>\n<pre class=\"prettyprint linenums\" ><code class=\"language-java\">\/\/ \u7ebf\u7a0b A\nmap.computeIfAbsent(key, k -&gt; value);\n\/\/ \u7ebf\u7a0b B\nmap.computeIfAbsent(key, k -&gt; anotherValue);<\/code><\/pre>\n<p>\u5f88\u591a\u540c\u5b66\u53ef\u80fd\u4f1a\u8bf4\u4e86\uff0c\u8fd9\u79cd\u60c5\u51b5\u4e5f\u80fd\u52a0\u9501\u540c\u6b65\u5440\uff01\u786e\u5b9e\u53ef\u4ee5\uff0c\u4f46\u4e0d\u5efa\u8bae\u4f7f\u7528\u52a0\u9501\u7684\u540c\u6b65\u673a\u5236\uff0c\u8fdd\u80cc\u4e86\u4f7f\u7528 ConcurrentHashMap \u7684\u521d\u8877\u3002\u5728\u4f7f\u7528 ConcurrentHashMap \u7684\u65f6\u5019\uff0c\u5c3d\u91cf\u4f7f\u7528\u8fd9\u4e9b\u539f\u5b50\u6027\u7684\u590d\u5408\u64cd\u4f5c\u65b9\u6cd5\u6765\u4fdd\u8bc1\u539f\u5b50\u6027\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Java \u96c6\u5408\u6982\u89c8 Java \u96c6\u5408\uff0c\u4e5f\u53eb\u4f5c\u5bb9\u5668\uff0c\u4e3b\u8981\u662f\u7531\u4e24\u5927\u63a5\u53e3\u6d3e\u751f\u800c\u6765\uff1a\u4e00\u4e2a\u662f Collection\u63a5\u53e3\uff0c\u4e3b\u8981\u7528\u4e8e\u5b58\u653e\u5355\u4e00\u5143\u7d20\uff1b\u53e6\u4e00\u4e2a\u662f Map \u63a5\u53e3\uff0c\u4e3b\u8981\u7528\u4e8e\u5b58\u653e\u952e\u503c\u5bf9\u3002\u5bf9\u4e8eCollection \u63a5\u53e3\uff0c\u4e0b\u9762\u53c8\u6709\u4e09\u4e2a\u4e3b\u8981\u7684\u5b50\u63a5\u53e3\uff1aList\u3001Set \u3001 Queue\u3002 \u8bf4\u8bf4 List, Set, Queue, Map \u56db\u8005\u7684\u533a\u522b\uff1f List(\u5bf9\u4ed8\u987a\u5e8f\u7684\u597d\u5e2e\u624b): \u5b58\u50a8\u7684\u5143\u7d20\u662f\u6709\u5e8f\u7684\u3001\u53ef\u91cd\u590d\u7684\u3002 Se 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