![\"\"](\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2026\/01\/20260128140846-697a186e89936.png\")
<\/p>\n\u9996\u5148\u9700\u77e5HashMap\u7684\u6570\u636e\u7ed3\u6784\u4e3a：\u54c8\u5e0c\u8868\u3001\u94fe\u8868\u3001\u7ea2\u9ed1\u6811<\/p>\n
<\/p>\n
\u5411HashMap\u4fdd\u5b58\u4e00\u4e2akey-value\u952e\u503c\u5bf9\u65f6\u91cd\u70b9\u4f7f\u7528putVal（）\u65b9\u6cd5<\/p>\n
\u5728putVal（）\u65b9\u6cd5\u4e2d\u4f1a\u5b9a\u4e49：tab\u8868\u793a\u5b58\u5165，p\u8868\u793a\u54c8\u5e0c\u8868\u4e2d\u5df2\u6709<\/p>\n
Node<K,V>[] tab; Node<K,V> p<\/p>\n
\u00a0 HashMap\u5728\u5b58\u5165\u4e00\u4e2a\u503c\u65f6，\u4f1a\u5148\u68c0\u67e5\u5b9a\u4e49\u7684HashMap\u7684\u5bb9\u91cf\u662f\u5426\u4e3a0\u6216null，\u5982\u679c\u662f\u5176\u4e2d\u7684\u4e00\u79cd\u53ef\u80fd，resize\u4e2d\u6709\u5e38\u91cfDEFAULT_INITIAL_CAPACITY，\u5219\u5c06\u521d\u59cb\u5bb9\u91cf\u8bbe\u5b9a\u4e3a16\u3002<\/p>\n
if ((tab = table) == null || (n = tab.length) == 0)
\n n = (tab = resize()).length;<\/p>\n
\u63a5\u4e0b\u6765\u4f1a\u901a\u8fc7hash\u503c\u6765\u8ba1\u7b97\u5e94\u5b58\u5728\u54c8\u5e0c\u8868\u4e2d\u7684\u4e0b\u6807\u4f4d\u7f6e，\u6b64\u4e0b\u6807\u4f4d\u7f6e\u5982\u679c\u5728\u54c8\u5e0c\u8868\u4e2d\u7684\u503c\u4e3anull，\u90a3\u4e48\u5c31\u5c06tab\u4e2d\u7684\u503c\u5b58\u8fdbnewNode\u4e2d（\u54c8\u5e0c\u503c，key\u503c，value\u503c，next）\u3002<\/p>\n
if ((p = tab[i = (n – 1) & hash]) == null)
\n tab[i] = newNode(hash, key, value, null);<\/p>\n
\u6b64\u4e0b\u6807\u4f4d\u7f6e\u4e0d\u4e3a\u7a7a，\u5982\u679c\u6709\u540c\u6837\u7684\u54c8\u5e0c\u503c\u4e14key\u7684\u5185\u5bb9\u76f8\u540c，\u6216key\u4e0d\u4e3a\u7a7a\u4e14key\u503c\u5df2\u5b58\u5728，\u5219\u5c06\u65e7\u7684value\u503c\u66ff\u6362\u4e3a\u65b0\u7684value\u503c\u3002<\/p>\n
else {
\n Node<K,V> e; K k;
\n if (p.hash == hash &&
\n ((k = p.key) == key || (key != null && key.equals(k))))
\n e = p;<\/p>\n
\u6b64\u4e0b\u6807\u4f4d\u7f6e\u4e0d\u4e3a\u7a7a\u4e14key\u4e0d\u91cd\u590d，\u5219\u68c0\u67e5p\u662f\u5426\u5b58\u5728\u7ea2\u9ed1\u6811\u4e2d，\u5728\u6811\u4e2d，\u5219\u5c06\u952e\u503c\u5bf9\u5b58\u5165\u7ea2\u9ed1\u6811\u4e2d\u3002
\nelse if (p instanceof TreeNode)
\n e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);<\/p>\n
\u6b64\u4e0b\u6807\u4f4d\u7f6e\u4e0d\u4e3a\u7a7a\u4e14key\u4e0d\u91cd\u590d，p\u4e0d\u5b58\u5728\u7ea2\u9ed1\u6811\u4e2d，\u5219\u5224\u65ad\u5f53\u524d\u4e0b\u6807\u7684next\u662f\u5426\u4e3a\u7a7a，\u4e3a\u7a7a\u5219\u5c06\u503c\u5b58\u5230next\u4e2d，\u540c\u65f6\u9700\u8981\u68c0\u67e5，\u6dfb\u52a0\u65b0\u952e\u503c\u5bf9\u540e\u4f1a\u4e0d\u4f1a\u4ea7\u751f\u7ea2\u9ed1\u6811，\u6761\u4ef6\u4e3a\u6b64\u94fe\u8868\u957f\u5ea6\u5927\u4e8e8\u4e14\u6570\u7ec4\u5bb9\u91cf\u5927\u4e8e64，\u6ee1\u8db3\u6761\u4ef6\u5219\u4ea7\u751f\u7ea2\u9ed1\u6811，\u540c\u65f6\u5728\u94fe\u8868\u4e2d\u68c0\u67e5\u5230\u7684\u76f8\u540c\u7684key\u4e5f\u8fdb\u884c\u66ff\u6362\u64cd\u4f5c\u3002<\/p>\n
else {
\n for (int binCount = 0; ; ++binCount) {
\n if ((e = p.next) == null) {
\n p.next = newNode(hash, key, value, null);
\n if (binCount >= TREEIFY_THRESHOLD – 1) \/\/ -1 for 1st
\n treeifyBin(tab, hash);
\n break;
\n }
\n if (e.hash == hash &&
\n ((k = e.key) == key || (key != null && key.equals(k))))
\n break;
\n p = e;
\n }
\n}<\/p>\n
\u540c\u65f6\u5728\u66ff\u6362\u64cd\u4f5c\u65f6，\u7528\u65b0\u7684value\u66ff\u6362\u65e7\u7684value，\u53ef\u8fd4\u56de\u4e00\u4e2a\u65e7\u7684value\u503coldValue<\/p>\n
if (e != null) { \/\/ existing mapping for key
\n V oldValue = e.value;
\n if (!onlyIfAbsent || oldValue == null)
\n e.value = value;
\n afterNodeAccess(e);
\n return oldValue;
\n}<\/p>\n
\u5728putVal（）\u65b9\u6cd5\u7684\u6700\u540e\u4f1a\u4f7f\u7528resize\u65b9\u6cd5\u7528\u6765\u8fbe\u5230\u5b58\u50a8\u8fc7\u7a0b\u4e2d\u6269\u5bb9\u7684\u9700\u6c42，\u6bcf\u6b21\u6269\u5bb9\u540e\u7684\u5bb9\u91cf\u662f\u6269\u5bb9\u524d\u7684\u4e8c\u500d，\u7b80\u5355\u8bb2\u4e00\u4e0b\u6269\u5bb9\u6761\u4ef6：<\/p>\n
\u7b2c\u4e00\u79cd\u60c5\u51b5：\u5728\u7b2c\u4e00\u6b21\u5b58\u5165\u503c\u65f6\u5c06\u521d\u59cb\u5bb9\u91cf\u6269\u5bb9\u4e3a16，\u524d\u9762\u63d0\u5230\u8fc7\u3002<\/p>\n
\u7b2c\u4e8c\u79cd\u60c5\u51b5：\u5728\u5355\u6761\u94fe\u8868\u957f\u5ea6\u8fbe\u52308\u4e14\u6570\u7ec4\u5bb9\u91cf\u5c0f\u4e8e64\u65f6\u4f1a\u6269\u5bb9\u4e00\u6b21，\u907f\u514d\u7ea2\u9ed1\u6811\u8f7b\u6613\u4ea7\u751f\u5e26\u6765\u7684\u7ef4\u62a4\u6210\u672c\u3002<\/p>\n
\u7b2c\u4e09\u79cd\u60c5\u51b5：HashMap\u4e2d\u7684\u5143\u7d20\u4e2a\u6570\u8d85\u8fc7threshold\u6269\u5bb9\u9608\u503c，threshold = \u6570\u7ec4\u5bb9\u91cf * \u52a0\u8f7d\u56e0\u5b50\u3002\u52a0\u8f7d\u56e0\u5b50\u521d\u59cb\u503c\u4e3a0.75，\u53ef\u81ea\u5b9a\u4e49\u3002<\/p>\n
++modCount;
\nif (++size > threshold)
\n resize();
\nafterNodeInsertion(evict);
\nreturn null;<\/p>\n","protected":false},"excerpt":{"rendered":"
\u9996\u5148\u9700\u77e5HashMap\u7684\u6570\u636e\u7ed3\u6784\u4e3a：\u54c8\u5e0c\u8868\u3001\u94fe\u8868\u3001\u7ea2\u9ed1\u6811\u5411HashMap\u4fdd\u5b58\u4e00\u4e2akey-value\u952e\u503c\u5bf9\u65f6\u91cd\u70b9\u4f7f\u7528putVal（）\u65b9\u6cd5\u5728putVal（）\u65b9\u6cd5\u4e2d\u4f1a\u5b9a\u4e49：tab\u8868\u793a\u5b58\u5165，p\u8868\u793a\u54c8\u5e0c\u8868\u4e2d\u5df2\u6709Node[] tab; Node pHashMap\u5728\u5b58\u5165\u4e00\u4e2a\u503c\u65f6，\u4f1a\u5148\u68c0\u67e5\u5b9a\u4e49\u7684HashMap\u7684\u5bb9\u91cf\u662f\u5426\u4e3a0\u6216null，\u5982\u679c\u662f\u5176\u4e2d\u7684\u4e00<\/p>\n","protected":false},"author":2,"featured_media":67540,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[99,190],"topic":[],"class_list":["post-67541","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-server","tag-java","tag-190"],"yoast_head":"\n