\n| \n > 0<\/p>\n<\/td>\n | \n \u521d\u59cb\u5316\u5b8c\u6210\u540e\u7684\u6269\u5bb9\u9608\u503c（\u5bb9\u91cf \u00d7 0.75）<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n \u56db\u3001\u6784\u9020\u65b9\u6cd5：\u5ef6\u8fdf\u521d\u59cb\u5316<\/h3>\nConcurrentHashMap \u91c7\u7528\u4e86\u5ef6\u8fdf\u521d\u59cb\u5316\u7b56\u7565\u2014\u2014\u6784\u9020\u65b9\u6cd5\u53ea\u8ba1\u7b97\u5bb9\u91cf，\u5e76\u4e0d\u771f\u6b63\u521b\u5efa table \u6570\u7ec4\u3002<\/p>\n \/\/ \u65e0\u53c2\u6784\u9020：\u4ec0\u4e48\u4e5f\u4e0d\u505a
\npublic ConcurrentHashMap() { }<\/p>\n \/\/ \u6307\u5b9a\u521d\u59cb\u5bb9\u91cf\u7684\u6784\u9020\u65b9\u6cd5
\npublic ConcurrentHashMap(int initialCapacity) {
\n if (initialCapacity < 0)
\n throw new IllegalArgumentException();
\n \/\/ \u8ba1\u7b97\u5927\u4e8e 1.5 * initialCapacity + 1 \u7684\u6700\u5c0f 2 \u7684\u5e42
\n int cap = tableSizeFor(initialCapacity + (initialCapacity >>> 1) + 1);
\n this.sizeCtl = cap; \/\/ \u53ea\u8bbe\u7f6e sizeCtl，\u4e0d\u521b\u5efa table
\n}<\/p>\n \u5ef6\u8fdf\u521d\u59cb\u5316\u7684\u597d\u5904：\u53ea\u6709\u5728\u7b2c\u4e00\u6b21 put \u65f6\u624d\u771f\u6b63\u521b\u5efa\u6570\u7ec4，\u907f\u514d\u4e86\u4e0d\u5fc5\u8981\u7684\u5185\u5b58\u5360\u7528\u3002<\/p>\n tableSizeFor \u65b9\u6cd5\u786e\u4fdd\u5bb9\u91cf\u59cb\u7ec8\u662f 2 \u7684\u5e42，\u8fd9\u662f\u4e3a\u4e86\u540e\u7eed\u4f7f\u7528\u4f4d\u8fd0\u7b97（(n – 1) & hash）\u66ff\u4ee3\u53d6\u6a21\u8fd0\u7b97，\u63d0\u5347\u6027\u80fd\u3002<\/p>\n \u6ce8\u610f：loadFactor \u867d\u7136\u5728\u6784\u9020\u65b9\u6cd5\u4e2d\u4f5c\u4e3a\u53c2\u6570\u4f20\u5165，\u4f46\u8ba1\u7b97\u5b8c size \u540e\u5e76\u672a\u88ab\u4fdd\u5b58\u4e3a\u6210\u5458\u53d8\u91cf，\u540e\u7eed\u6269\u5bb9\u9608\u503c\u8ba1\u7b97\u56fa\u5b9a\u4f7f\u7528 0.75\u3002<\/p>\n \u4e94\u3001put \u65b9\u6cd5：\u7ebf\u7a0b\u5b89\u5168\u7684\u6838\u5fc3<\/h3>\nput \u65b9\u6cd5\u662f ConcurrentHashMap \u6700\u590d\u6742\u7684\u90e8\u5206，\u6d89\u53ca\u521d\u59cb\u5316\u3001CAS \u63d2\u5165\u3001\u9501\u6269\u5bb9\u3001\u94fe\u8868\/\u6811\u64cd\u4f5c\u7b49\u591a\u4e2a\u73af\u8282\u3002<\/p>\n 5.1 \u5165\u53e3\u4e0e hash \u8ba1\u7b97<\/h4>\npublic V put(K key, V value) {
\n return putVal(key, value, false);
\n}<\/p>\n final V putVal(K key, V value, boolean onlyIfAbsent) {
\n \/\/ key \u548c value \u90fd\u4e0d\u80fd\u4e3a null
\n if (key == null || value == null) throw new NullPointerException();<\/p>\n \/\/ spread：\u8ba9\u9ad8\u4f4d\u53c2\u4e0e\u5bfb\u5740，\u4f7f hash \u66f4\u5206\u6563
\n int hash = spread(key.hashCode());
\n int binCount = 0; \/\/ \u8bb0\u5f55\u6876\u4e2d\u5143\u7d20\u4e2a\u6570，\u7528\u4e8e\u5224\u65ad\u662f\u5426\u6811\u5316<\/p>\n \/\/ \u81ea\u65cb（\u65e0\u9650\u5faa\u73af），\u76f4\u5230\u64cd\u4f5c\u6210\u529f
\n for (Node<K,V>[] tab = table;;) {
\n Node<K,V> f; int n, i, fh;
\n \/\/ … \u56db\u79cd\u60c5\u51b5\u5904\u7406
\n }
\n}<\/p>\n spread \u65b9\u6cd5\u5c06 key.hashCode() \u7684\u9ad8\u4f4d\u4e0e\u4f4e\u4f4d\u6df7\u5408，\u51cf\u5c11 hash \u51b2\u7a81：<\/p>\n static final int spread(int h) {
\n return (h ^ (h >>> 16)) & HASH_BITS;
\n}<\/p>\n 5.2 \u56db\u79cd\u60c5\u51b5\u5904\u7406<\/h4>\nputVal \u7684\u6838\u5fc3\u662f\u4e00\u4e2a\u81ea\u65cb\u5faa\u73af，\u5904\u7406\u56db\u79cd\u4e0d\u540c\u7684\u60c5\u51b5：<\/p>\n Case 1：table \u672a\u521d\u59cb\u5316<\/h5>\nif (tab == null || (n = tab.length) == 0)
\n tab = initTable(); \/\/ \u521d\u59cb\u5316 table<\/p>\n initTable() \u901a\u8fc7 CAS \u63a7\u5236 sizeCtl，\u786e\u4fdd\u53ea\u6709\u4e00\u4e2a\u7ebf\u7a0b\u6267\u884c\u521d\u59cb\u5316：<\/p>\n private final Node<K,V>[] initTable() {
\n Node<K,V>[] tab; int sc;
\n while ((tab = table) == null || tab.length == 0) {
\n if ((sc = sizeCtl) < 0) \/\/ \u5176\u4ed6\u7ebf\u7a0b\u6b63\u5728\u521d\u59cb\u5316
\n Thread.yield();
\n else if (U.compareAndSetInt(this, SIZECTL, sc, -1)) {
\n \/\/ CAS \u5c06 sizeCtl \u8bbe\u4e3a -1，\u5f53\u524d\u7ebf\u7a0b\u83b7\u5f97\u521d\u59cb\u5316\u6743
\n try {
\n if ((tab = table) == null || tab.length == 0) {
\n int n = (sc > 0) ? sc : DEFAULT_CAPACITY;
\n Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n];
\n table = tab = nt;
\n sc = n – (n >>> 2); \/\/ 0.75 * n
\n }
\n } finally {
\n sizeCtl = sc; \/\/ \u8bbe\u7f6e\u6269\u5bb9\u9608\u503c
\n }
\n break;
\n }
\n }
\n return tab;
\n}<\/p>\n Case 2：\u6876\u4f4d\u4e3a\u7a7a（\u65e0 hash \u51b2\u7a81）<\/h5>\nelse if ((f = tabAt(tab, i = (n – 1) & hash)) == null) {
\n \/\/ \u4f7f\u7528 CAS \u5c06\u65b0\u8282\u70b9\u653e\u5165\u7a7a\u6876\u4f4d
\n if (casTabAt(tab, i, null, new Node<K,V>(hash, key, value, null)))
\n break; \/\/ CAS \u6210\u529f，\u8df3\u51fa\u5faa\u73af
\n}<\/p>\n \u8fd9\u91cc\u4f7f\u7528 CAS \u65e0\u9501\u64cd\u4f5c，\u4e0d\u9700\u8981\u52a0\u9501，\u662f\u6700\u9ad8\u6548\u7684\u63d2\u5165\u573a\u666f\u3002<\/p>\n Case 3：\u6876\u4f4d\u6b63\u5728\u6269\u5bb9（FWD \u8282\u70b9）<\/h5>\nelse if ((fh = f.hash) == MOVED)
\n tab = helpTransfer(tab, f); \/\/ \u5f53\u524d\u7ebf\u7a0b\u534f\u52a9\u6269\u5bb9<\/p>\n \u5982\u679c\u6876\u4f4d\u7684\u5934\u8282\u70b9\u662f ForwardingNode（hash == MOVED），\u8bf4\u660e\u8be5\u6876\u6b63\u5728\u6269\u5bb9\u8fc1\u79fb，\u5f53\u524d\u7ebf\u7a0b\u4f1a\u534f\u52a9\u6269\u5bb9\u3002<\/p>\n Case 4：\u6b63\u5e38\u63d2\u5165（\u94fe\u8868\u6216\u7ea2\u9ed1\u6811）<\/h5>\nelse {
\n V oldVal = null;
\n synchronized (f) { \/\/ \u9501\u4f4f\u5934\u8282\u70b9
\n if (tabAt(tab, i) == f) { \/\/ \u53cc\u91cd\u68c0\u67e5
\n if (fh >= 0) { \/\/ \u666e\u901a\u94fe\u8868\u8282\u70b9
\n binCount = 1;
\n for (Node<K,V> e = f;; ++binCount) {
\n K ek;
\n if (e.hash == hash &&
\n ((ek = e.key) == key || (ek != null && key.equals(ek)))) {
\n oldVal = e.val;
\n if (!onlyIfAbsent) e.val = value;
\n break;
\n }
\n Node<K,V> pred = e;
\n if ((e = e.next) == null) {
\n pred.next = new Node<K,V>(hash, key, value, null);
\n break;
\n }
\n }
\n } else if (f instanceof TreeBin) { \/\/ \u7ea2\u9ed1\u6811\u8282\u70b9
\n Node<K,V> p;
\n binCount = 2;
\n if ((p = ((TreeBin<K,V>)f).putTreeVal(hash, key, value)) != null) {
\n oldVal = p.val;
\n if (!onlyIfAbsent) p.val = value;
\n }
\n }
\n }
\n }
\n \/\/ \u5224\u65ad\u662f\u5426\u9700\u8981\u6811\u5316
\n if (binCount != 0) {
\n if (binCount >= TREEIFY_THRESHOLD) \/\/ >= 8
\n treeifyBin(tab, i);
\n if (oldVal != null) return oldVal;
\n break;
\n }
\n}<\/p>\n \u5173\u952e\u8bbe\u8ba1：\u4f7f\u7528 synchronized \u9501\u4f4f\u6876\u7684\u5934\u8282\u70b9（f），\u800c\u4e0d\u662f\u9501\u6574\u5f20\u8868\u3002\u8fd9\u610f\u5473\u7740\u53ea\u6709\u64cd\u4f5c\u540c\u4e00\u4e2a\u6876\u7684\u7ebf\u7a0b\u624d\u4f1a\u7ade\u4e89\u9501，\u4e0d\u540c\u6876\u7684\u64cd\u4f5c\u5b8c\u5168\u5e76\u884c\u3002<\/p>\n 5.3 addCount：\u5143\u7d20\u8ba1\u6570\u4e0e\u6269\u5bb9\u89e6\u53d1<\/h4>\n\u63d2\u5165\u5b8c\u6210\u540e，\u8c03\u7528 addCount \u589e\u52a0\u5143\u7d20\u6570\u91cf，\u5e76\u68c0\u67e5\u662f\u5426\u9700\u8981\u6269\u5bb9：<\/p>\n addCount(1L, binCount);<\/p>\n addCount \u5185\u90e8\u4f1a\u5224\u65ad\u5f53\u524d\u5143\u7d20\u6570\u91cf\u662f\u5426\u8d85\u8fc7 sizeCtl（\u6269\u5bb9\u9608\u503c），\u5982\u679c\u8d85\u8fc7\u5219\u89e6\u53d1 transfer \u6269\u5bb9\u3002<\/p>\n \u516d\u3001get \u65b9\u6cd5：\u65e0\u9501\u8bfb\u53d6\u7684\u79d8\u5bc6<\/h3>\nget \u65b9\u6cd5\u662f ConcurrentHashMap \u6027\u80fd\u7684\u53c8\u4e00\u4f53\u73b0\u2014\u2014\u5168\u7a0b\u4e0d\u52a0\u9501\u3002<\/p>\n public V get(Object key) {
\n Node<K,V>[] tab; Node<K,V> e, p; int n, eh; K ek;
\n int h = spread(key.hashCode());
\n if ((tab = table) != null && (n = tab.length) > 0 &&
\n (e = tabAt(tab, (n – 1) & h)) != null) {<\/p>\n if ((eh = e.hash) == h) {
\n \/\/ \u60c5\u51b51：\u9996\u8282\u70b9\u5c31\u662f\u76ee\u6807\u8282\u70b9
\n if ((ek = e.key) == key || (ek != null && key.equals(ek)))
\n return e.val;
\n }
\n else if (eh < 0) {
\n \/\/ \u60c5\u51b52：hash < 0，\u53ef\u80fd\u662f TreeBin \u6216 ForwardingNode
\n \/\/ – \u5982\u679c\u662f ForwardingNode（\u6269\u5bb9\u4e2d），\u53bb nextTable \u4e2d\u67e5\u627e
\n \/\/ – \u5982\u679c\u662f TreeBin，\u904d\u5386\u7ea2\u9ed1\u6811
\n return (p = e.find(h, key)) != null ? p.val : null;
\n }
\n \/\/ \u60c5\u51b53：\u904d\u5386\u94fe\u8868
\n while ((e = e.next) != null) {
\n if (e.hash == h &&
\n ((ek = e.key) == key || (ek != null && key.equals(ek))))
\n return e.val;
\n }
\n }
\n return null;
\n}<\/p>\n \u4e3a\u4ec0\u4e48 get \u4e0d\u9700\u8981\u52a0\u9501？<\/h4>\n\nvolatile \u4fdd\u8bc1\u53ef\u89c1\u6027：Node \u7684 val \u548c next \u90fd\u662f volatile \u7684，\u5199\u5165\u7684\u7ed3\u679c\u5bf9\u6240\u6709\u7ebf\u7a0b\u7acb\u5373\u53ef\u89c1<\/p>\n<\/li>\n \ntable \u662f volatile \u7684：\u6570\u7ec4\u5f15\u7528\u672c\u8eab\u4fdd\u8bc1\u53ef\u89c1\u6027<\/p>\n<\/li>\n \nNode \u7684 hash \u548c key \u662f final \u7684：\u4e00\u65e6\u521b\u5efa\u4e0d\u53ef\u53d8<\/p>\n<\/li>\n \n\u6269\u5bb9\u65f6\u7684\u7279\u6b8a\u5904\u7406：\u901a\u8fc7 ForwardingNode.find() \u5230\u65b0\u8868\u67e5\u627e<\/p>\n<\/li>\n \u8fd9\u79cd\u8bbe\u8ba1\u4f7f\u5f97 get \u64cd\u4f5c\u51e0\u4e4e\u4e0d\u53d7\u9501\u7ade\u4e89\u5f71\u54cd，\u6027\u80fd\u6781\u9ad8\u3002<\/p>\n \u4e03\u3001\u6269\u5bb9\u673a\u5236：\u591a\u7ebf\u7a0b\u534f\u540c\u4f5c\u6218<\/h3>\n\u6269\u5bb9\u662f ConcurrentHashMap \u6700\u590d\u6742\u7684\u90e8\u5206，\u4e5f\u662f\u5b83\u533a\u522b\u4e8e\u666e\u901a HashMap \u7684\u6838\u5fc3\u4f18\u52bf\u2014\u2014\u652f\u6301\u591a\u7ebf\u7a0b\u534f\u540c\u6269\u5bb9\u3002<\/p>\n 7.1 \u6269\u5bb9\u89e6\u53d1\u6761\u4ef6<\/h4>\n\u6269\u5bb9\u5728 addCount \u65b9\u6cd5\u4e2d\u88ab\u89e6\u53d1：<\/p>\n if (check >= 0) {
\n Node<K,V>[] tab, nt; int n, sc;
\n while (s >= (long)(sc = sizeCtl) && (tab = table) != null &&
\n (n = tab.length) < MAXIMUM_CAPACITY) {
\n int rs = resizeStamp(n);
\n if (sc < 0) { \/\/ \u5df2\u6709\u7ebf\u7a0b\u5728\u6269\u5bb9
\n if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||
\n sc == rs + MAX_RESIZERS || (nt = nextTable) == null ||
\n transferIndex <= 0)
\n break;
\n if (U.compareAndSetInt(this, SIZECTL, sc, sc + 1))
\n transfer(tab, nt); \/\/ \u5f53\u524d\u7ebf\u7a0b\u534f\u52a9\u6269\u5bb9
\n }
\n else if (U.compareAndSetInt(this, SIZECTL, sc,
\n (rs << RESIZE_STAMP_SHIFT) + 2))
\n transfer(tab, null); \/\/ \u5f53\u524d\u7ebf\u7a0b\u662f\u7b2c\u4e00\u4e2a\u53d1\u8d77\u6269\u5bb9\u7684
\n s = sumCount();
\n }
\n}<\/p>\n 7.2 transfer：\u6570\u636e\u8fc1\u79fb<\/h4>\ntransfer \u65b9\u6cd5\u8d1f\u8d23\u5c06\u65e7 table \u7684\u6570\u636e\u8fc1\u79fb\u5230\u65b0 table（\u5bb9\u91cf\u7ffb\u500d）：<\/p>\n private final void transfer(Node<K,V>[] tab, Node<K,V>[] nextTab) {
\n int n = tab.length, stride;
\n \/\/ \u8ba1\u7b97\u6bcf\u4e2a\u7ebf\u7a0b\u8d1f\u8d23\u7684\u6876\u4f4d\u6570（\u6b65\u957f）
\n if ((stride = (NCPU > 1) ? (n >>> 3) \/ NCPU : n) < MIN_TRANSFER_STRIDE)
\n stride = MIN_TRANSFER_STRIDE; \/\/ \u6700\u5c0f 16<\/p>\n if (nextTab == null) { \/\/ \u7b2c\u4e00\u4e2a\u53d1\u8d77\u6269\u5bb9\u7684\u7ebf\u7a0b\u521b\u5efa\u65b0\u6570\u7ec4
\n try {
\n Node<K,V>[] nt = (Node<K,V>[])new Node<?,?>[n << 1]; \/\/ \u5bb9\u91cf\u7ffb\u500d
\n nextTab = nt;
\n } catch (Throwable ex) {
\n sizeCtl = Integer.MAX_VALUE;
\n return;
\n }
\n nextTable = nextTab;
\n transferIndex = n; \/\/ \u4ece\u6700\u540e\u4e00\u4e2a\u6876\u5f00\u59cb\u5206\u914d\u4efb\u52a1
\n }<\/p>\n int nextn = nextTab.length;
\n ForwardingNode<K,V> fwd = new ForwardingNode<K,V>(nextTab);
\n boolean advance = true;
\n boolean finishing = false;<\/p>\n \/\/ \u81ea\u65cb\u8fc1\u79fb\u6570\u636e
\n for (int i = 0, bound = 0;;) {
\n \/\/ … \u5206\u914d\u4efb\u52a1\u3001\u8fc1\u79fb\u6570\u636e …
\n }
\n}<\/p>\n 7.3 \u6269\u5bb9\u7684\u6838\u5fc3\u8bbe\u8ba1\u8981\u70b9<\/h4>\n\n\u4efb\u52a1\u5206\u7247：\u6bcf\u4e2a\u7ebf\u7a0b\u6bcf\u6b21\u8d1f\u8d23 stride \u4e2a\u6876\u7684\u8fc1\u79fb（\u9ed8\u8ba4 16）<\/p>\n<\/li>\n \n\u4ece\u540e\u5f80\u524d\u8fc1\u79fb：transferIndex \u8bb0\u5f55\u5168\u5c40\u8fc1\u79fb\u8fdb\u5ea6，\u4ece\u9ad8\u4f4d\u5411\u4f4e\u4f4d\u63a8\u8fdb<\/p>\n<\/li>\n \nFWD \u6807\u8bb0：\u8fc1\u79fb\u5b8c\u6210\u7684\u6876\u4f4d\u8bbe\u7f6e\u4e3a ForwardingNode，hash \u503c\u4e3a MOVED<\/p>\n<\/li>\n \n\u94fe\u8868\u62c6\u5206：\u539f\u94fe\u8868\u88ab\u62c6\u5206\u4e3a\u4e24\u4e2a\u94fe\u8868，\u5206\u522b\u653e\u5165\u65b0\u8868\u7684 i \u548c i + n \u4f4d\u7f6e<\/p>\n<\/li>\n \nCAS \u63a7\u5236\u5e76\u53d1：\u901a\u8fc7 CAS \u4fee\u6539 sizeCtl \u548c transferIndex \u534f\u8c03\u591a\u7ebf\u7a0b<\/p>\n<\/li>\n \u591a\u7ebf\u7a0b\u6269\u5bb9\u7684\u4f18\u52bf：\u6269\u5bb9\u65f6\u95f4\u968f\u7740\u53c2\u4e0e\u7ebf\u7a0b\u6570\u589e\u52a0\u800c\u7f29\u77ed，\u5145\u5206\u5229\u7528\u591a\u6838 CPU \u80fd\u529b\u3002<\/p>\n \u516b\u3001\u94fe\u8868 \u2194 \u7ea2\u9ed1\u6811\u8f6c\u6362<\/h3>\n8.1 \u94fe\u8868\u8f6c\u7ea2\u9ed1\u6811<\/h4>\n\u5f53\u94fe\u8868\u957f\u5ea6 \u2265 8 \u4e14\u6570\u7ec4\u957f\u5ea6 \u2265 64 \u65f6，\u94fe\u8868\u8f6c\u6362\u4e3a\u7ea2\u9ed1\u6811：<\/p>\n private final void treeifyBin(Node<K,V>[] tab, int index) {
\n Node<K,V> b; int n, sc;
\n if (tab != null) {
\n if ((n = tab.length) < MIN_TREEIFY_CAPACITY) \/\/ < 64
\n tryPresize(n << 1); \/\/ \u4f18\u5148\u6269\u5bb9
\n else if ((b = tabAt(tab, index)) != null && b.hash >= 0) {
\n synchronized (b) {
\n if (tabAt(tab, index) == b) {
\n \/\/ \u5c06\u94fe\u8868\u8282\u70b9\u8f6c\u4e3a TreeNode，\u7136\u540e\u6784\u5efa\u7ea2\u9ed1\u6811
\n TreeNode<K,V> hd = null, tl = null;
\n for (Node<K,V> e = b; e != null; e = e.next) {
\n TreeNode<K,V> p = new TreeNode<K,V>(e.hash, e.key, e.val, null, null);
\n if ((p.prev = tl) == null) hd = p;
\n else tl.next = p;
\n tl = p;
\n }
\n \/\/ \u7528 TreeBin \u66ff\u4ee3\u539f\u94fe\u8868\u5934\u8282\u70b9
\n setTabAt(tab, index, new TreeBin<K,V>(hd));
\n }
\n }
\n }
\n }
\n}<\/p>\n \u4e3a\u4ec0\u4e48\u9608\u503c\u662f 8？ \u6e90\u7801\u6ce8\u91ca\u6307\u51fa，\u5728\u7406\u60f3\u60c5\u51b5\u4e0b，\u6876\u4e2d\u8282\u70b9\u6570\u670d\u4ece\u6cca\u677e\u5206\u5e03，\u4e00\u4e2a\u6876\u4e2d\u51fa\u73b0 8 \u4e2a\u8282\u70b9\u7684\u6982\u7387\u4ec5\u4e3a 0.00000006\u3002\u56e0\u6b64 8 \u662f\u4e00\u4e2a\u8db3\u591f\u4fdd\u5b88\u7684\u9608\u503c\u3002<\/p>\n 8.2 \u7ea2\u9ed1\u6811\u8f6c\u94fe\u8868<\/h4>\n\u5f53\u7ea2\u9ed1\u6811\u8282\u70b9\u6570\u51cf\u5c11\u5230 \u2264 6 \u65f6，\u6811\u9000\u5316\u4e3a\u94fe\u8868\u3002<\/p>\n \u4e5d\u3001\u603b\u7ed3<\/h3>\nConcurrentHashMap \u662f Java \u5e76\u53d1\u5bb9\u5668\u4e2d\u6700\u95ea\u8000\u7684\u660e\u661f，\u5b83\u7684\u8bbe\u8ba1\u4f53\u73b0\u4e86 Java \u5728\u5e76\u53d1\u7f16\u7a0b\u9886\u57df\u7684\u4e0d\u65ad\u8fdb\u6b65：<\/p>\n \u6838\u5fc3\u8981\u70b9\u56de\u987e<\/h4>\n\n\u6570\u636e\u7ed3\u6784：\u6570\u7ec4 + \u94fe\u8868 + \u7ea2\u9ed1\u6811，\u4e0e HashMap 1.8 \u4fdd\u6301\u4e00\u81f4<\/p>\n<\/li>\n \n\u7ebf\u7a0b\u5b89\u5168\u673a\u5236：CAS（\u65e0\u7ade\u4e89\u573a\u666f）+ synchronized（\u9501\u5934\u8282\u70b9），\u6452\u5f03\u4e86 Segment \u5206\u6bb5\u9501<\/p>\n<\/li>\n \n\u9501\u7c92\u5ea6：\u4ece Segment \u7ea7\u522b\u7ec6\u5316\u5230\u5355\u4e2a\u6876\u8282\u70b9，\u5e76\u53d1\u5ea6\u5927\u5e45\u63d0\u5347<\/p>\n<\/li>\n \n\u65e0\u9501\u8bfb\u53d6：get \u65b9\u6cd5\u5168\u7a0b\u4e0d\u52a0\u9501，\u4f9d\u8d56 volatile \u4fdd\u8bc1\u53ef\u89c1\u6027<\/p>\n<\/li>\n \n\u591a\u7ebf\u7a0b\u6269\u5bb9：\u652f\u6301\u591a\u7ebf\u7a0b\u534f\u540c\u5b8c\u6210\u6570\u636e\u8fc1\u79fb，\u5145\u5206\u5229\u7528\u591a\u6838 CPU<\/p>\n<\/li>\n \n\u5ef6\u8fdf\u521d\u59cb\u5316：table \u5728\u7b2c\u4e00\u6b21 put \u65f6\u624d\u771f\u6b63\u521b\u5efa<\/p>\n<\/li>\n \nput\u64cd\u4f5c\u6d41\u7a0b:\u9996\u5148\u5148\u5224\u65adkey\u548cvalue\u662f\u5426\u4e3a\u7a7a，\u5982\u679c\u4e3a\u7a7a，\u5219\u629b\u51fa\u5f02\u5e38，\u7136\u540e\u8ba1\u7b97\u54c8\u5e0c\u503c，\u8fdb\u5165\u81ea\u65cb\u64cd\u4f5c(CAS），\u5982\u679ctable\u4e3a\u7a7a，\u5219CAS\u521d\u59cb\u5316table，\u5982\u679c\u662f\u6b63\u5728\u6269\u5bb9，\u5219\u534f\u52a9\u6269\u5bb9，\u5982\u679c\u6876\u4e3a\u7a7a，\u5219\u76f4\u63a5CAS\u63d2\u5165，\u5982\u679c\u6876\u4f4d\u6709\u8282\u70b9，\u5219synchronized\u9501\u4f4f\u5934\u8282\u70b9，\u904d\u5386\u94fe\u8868，\u6709\u76f8\u540c\u7684\u5219\u66ff\u6362，\u6ca1\u6709\u5219\u63d2\u5165，\u7136\u540e\u5224\u65ad\u662f\u5426\u9700\u8981\u6811\u5316\u3002<\/p>\n<\/li>\n \nget\u64cd\u4f5c\u6d41\u7a0b:\u9996\u5148\u8ba1\u7b97\u54c8\u5e0c\u503c，\u5b9a\u4f4d\u6876，\u68c0\u67e5\u9996\u8282\u70b9，\u76f8\u540c\u5219\u76f4\u63a5\u8fd4\u56de，\u5982\u679c\u662ffwd\u6269\u5bb9\u4e2d \u5219\u53bbnextable\u4e2d\u5bfb\u627e，\u5982\u679c\u662ftreebin，\u5219\u53bb\u6811\u4e2d\u904d\u5386，\u5426\u5219\u53bb\u94fe\u8868\u4e2d\u904d\u5386\u3002<\/p>\n<\/li>\n \u6027\u80fd\u5bf9\u6bd4<\/h4>\n\n\n\n| \n \u5bb9\u5668<\/p>\n<\/td>\n | \n \u7ebf\u7a0b\u5b89\u5168<\/p>\n<\/td>\n | \n \u5e76\u53d1\u6027\u80fd<\/p>\n<\/td>\n | \n \u9002\u7528\u573a\u666f<\/p>\n<\/td>\n<\/tr>\n | \n| \n HashMap<\/p>\n<\/td>\n | \n \u274c<\/p>\n<\/td>\n | \n \u6700\u9ad8<\/p>\n<\/td>\n | \n \u5355\u7ebf\u7a0b\u73af\u5883<\/p>\n<\/td>\n<\/tr>\n | \n| \n Hashtable<\/p>\n<\/td>\n | \n \u2705（\u5168\u8868\u9501）<\/p>\n<\/td>\n | \n \u6781\u4f4e<\/p>\n<\/td>\n | \n \u9057\u7559\u4ee3\u7801<\/p>\n<\/td>\n<\/tr>\n | \n| \n ConcurrentHashMap (JDK 7)<\/p>\n<\/td>\n | \n \u2705（\u5206\u6bb5\u9501）<\/p>\n<\/td>\n | \n \u4e2d<\/p>\n<\/td>\n | \n \u4e2d\u7b49\u5e76\u53d1<\/p>\n<\/td>\n<\/tr>\n | \n| \n ConcurrentHashMap (JDK 8)<\/p>\n<\/td>\n | \n \u2705（CAS + \u9501\u5934\u8282\u70b9）<\/p>\n<\/td>\n | \n \u9ad8<\/p>\n<\/td>\n | \n \u9ad8\u5e76\u53d1\u9996\u9009<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n ConcurrentHashMap \u7684\u6210\u529f，\u6e90\u4e8e\u5b83\u5bf9\u5e76\u53d1\u6027\u80fd\u548c\u7ebf\u7a0b\u5b89\u5168\u7684\u7cbe\u5999\u5e73\u8861\u3002\u65e0\u8bba\u662f\u9762\u8bd5\u8fd8\u662f\u65e5\u5e38\u5f00\u53d1，\u6df1\u5165\u7406\u89e3\u5b83\u7684\u8bbe\u8ba1\u601d\u60f3，\u90fd\u80fd\u8ba9\u4f60\u5199\u51fa\u66f4\u9ad8\u6548\u3001\u66f4\u5b89\u5168\u7684\u5e76\u53d1\u4ee3\u7801\u3002<\/p>\n","protected":false},"excerpt":{"rendered":" \u4e00\u3001\u5f15\u8a00：HashMap \u7684\u7ebf\u7a0b\u5b89\u5168\u56f0\u5883HashMap \u662f Java \u4e2d\u6700\u5e38\u7528\u7684\u5bb9\u5668\u4e4b\u4e00，\u4f46\u5b83\u6709\u4e00\u4e2a\u81f4\u547d\u7f3a\u9677\u2014\u2014\u7ebf\u7a0b\u4e0d\u5b89\u5168\u3002\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b，HashMap \u5728\u6269\u5bb9\u65f6\u53ef\u80fd\u5f62\u6210\u73af\u5f62\u94fe\u8868，\u5bfc\u81f4 get() \u64cd\u4f5c\u9677\u5165\u6b7b\u5faa\u73af，CPU \u98d9\u5347\u5230 100%\u3002\u90a3\u7528 Hashtable \u5462？\u5b83\u6240\u6709\u65b9\u6cd5\u90fd\u52a0\u4e86 synchronized，\u76f8\u5f53\u4e8e\u7ed9\u6574\u5f20\u8868\u4e0a\u4e86\u4e00\u628a\u5927\u9501，\u540c\u4e00\u65f6\u523b\u53ea\u5141\u8bb8\u4e00\u4e2a\u7ebf\u7a0b\u64cd<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[99],"topic":[],"class_list":["post-88882","post","type-post","status-publish","format-standard","hentry","category-server","tag-java"],"yoast_head":"\n ConcurrentHashMap \u6df1\u5ea6\u89e3\u6790\uff1a\u4ece\u5206\u6bb5\u9501\u5230 CAS \u7684\u8fdb\u5316\u4e4b\u8def - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3<\/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.wsisp.com\/helps\/88882.html\" \/>\n<meta property=\"og:locale\" content=\"zh_CN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"ConcurrentHashMap \u6df1\u5ea6\u89e3\u6790\uff1a\u4ece\u5206\u6bb5\u9501\u5230 CAS \u7684\u8fdb\u5316\u4e4b\u8def - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"og:description\" content=\"\u4e00\u3001\u5f15\u8a00：HashMap \u7684\u7ebf\u7a0b\u5b89\u5168\u56f0\u5883HashMap \u662f Java \u4e2d\u6700\u5e38\u7528\u7684\u5bb9\u5668\u4e4b\u4e00，\u4f46\u5b83\u6709\u4e00\u4e2a\u81f4\u547d\u7f3a\u9677\u2014\u2014\u7ebf\u7a0b\u4e0d\u5b89\u5168\u3002\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b，HashMap \u5728\u6269\u5bb9\u65f6\u53ef\u80fd\u5f62\u6210\u73af\u5f62\u94fe\u8868，\u5bfc\u81f4 get() \u64cd\u4f5c\u9677\u5165\u6b7b\u5faa\u73af，CPU \u98d9\u5347\u5230 100%\u3002\u90a3\u7528 Hashtable \u5462？\u5b83\u6240\u6709\u65b9\u6cd5\u90fd\u52a0\u4e86 synchronized，\u76f8\u5f53\u4e8e\u7ed9\u6574\u5f20\u8868\u4e0a\u4e86\u4e00\u628a\u5927\u9501，\u540c\u4e00\u65f6\u523b\u53ea\u5141\u8bb8\u4e00\u4e2a\u7ebf\u7a0b\u64cd\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.wsisp.com\/helps\/88882.html\" \/>\n<meta property=\"og:site_name\" content=\"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"article:published_time\" content=\"2026-08-01T13:40:31+00:00\" \/>\n<meta name=\"author\" content=\"admin\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u4f5c\u8005\" \/>\n\t<meta name=\"twitter:data1\" content=\"admin\" \/>\n\t<meta name=\"twitter:label2\" content=\"\u9884\u8ba1\u9605\u8bfb\u65f6\u95f4\" \/>\n\t<meta name=\"twitter:data2\" content=\"8 \u5206\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/88882.html\",\"url\":\"https:\/\/www.wsisp.com\/helps\/88882.html\",\"name\":\"ConcurrentHashMap \u6df1\u5ea6\u89e3\u6790\uff1a\u4ece\u5206\u6bb5\u9501\u5230 CAS \u7684\u8fdb\u5316\u4e4b\u8def - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\",\"isPartOf\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/#website\"},\"datePublished\":\"2026-08-01T13:40:31+00:00\",\"dateModified\":\"2026-08-01T13:40:31+00:00\",\"author\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41\"},\"breadcrumb\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/88882.html#breadcrumb\"},\"inLanguage\":\"zh-Hans\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.wsisp.com\/helps\/88882.html\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/88882.html#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"\u9996\u9875\",\"item\":\"https:\/\/www.wsisp.com\/helps\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"ConcurrentHashMap \u6df1\u5ea6\u89e3\u6790\uff1a\u4ece\u5206\u6bb5\u9501\u5230 CAS \u7684\u8fdb\u5316\u4e4b\u8def\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/#website\",\"url\":\"https:\/\/www.wsisp.com\/helps\/\",\"name\":\"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\",\"description\":\"\u9999\u6e2f\u670d\u52a1\u5668_\u9999\u6e2f\u4e91\u670d\u52a1\u5668\u8d44\u8baf_\u670d\u52a1\u5668\u5e2e\u52a9\u6587\u6863_\u670d\u52a1\u5668\u6559\u7a0b\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/www.wsisp.com\/helps\/?s={search_term_string}\"},\"query-input\":\"required name=search_term_string\"}],\"inLanguage\":\"zh-Hans\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41\",\"name\":\"admin\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"zh-Hans\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery\",\"contentUrl\":\"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery\",\"caption\":\"admin\"},\"sameAs\":[\"http:\/\/wp.wsisp.com\"],\"url\":\"https:\/\/www.wsisp.com\/helps\/author\/admin\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"ConcurrentHashMap \u6df1\u5ea6\u89e3\u6790\uff1a\u4ece\u5206\u6bb5\u9501\u5230 CAS \u7684\u8fdb\u5316\u4e4b\u8def - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.wsisp.com\/helps\/88882.html","og_locale":"zh_CN","og_type":"article","og_title":"ConcurrentHashMap \u6df1\u5ea6\u89e3\u6790\uff1a\u4ece\u5206\u6bb5\u9501\u5230 CAS \u7684\u8fdb\u5316\u4e4b\u8def - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","og_description":"\u4e00\u3001\u5f15\u8a00：HashMap \u7684\u7ebf\u7a0b\u5b89\u5168\u56f0\u5883HashMap \u662f Java \u4e2d\u6700\u5e38\u7528\u7684\u5bb9\u5668\u4e4b\u4e00，\u4f46\u5b83\u6709\u4e00\u4e2a\u81f4\u547d\u7f3a\u9677\u2014\u2014\u7ebf\u7a0b\u4e0d\u5b89\u5168\u3002\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b，HashMap \u5728\u6269\u5bb9\u65f6\u53ef\u80fd\u5f62\u6210\u73af\u5f62\u94fe\u8868，\u5bfc\u81f4 get() \u64cd\u4f5c\u9677\u5165\u6b7b\u5faa\u73af，CPU \u98d9\u5347\u5230 100%\u3002\u90a3\u7528 Hashtable \u5462？\u5b83\u6240\u6709\u65b9\u6cd5\u90fd\u52a0\u4e86 synchronized，\u76f8\u5f53\u4e8e\u7ed9\u6574\u5f20\u8868\u4e0a\u4e86\u4e00\u628a\u5927\u9501，\u540c\u4e00\u65f6\u523b\u53ea\u5141\u8bb8\u4e00\u4e2a\u7ebf\u7a0b\u64cd","og_url":"https:\/\/www.wsisp.com\/helps\/88882.html","og_site_name":"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","article_published_time":"2026-08-01T13:40:31+00:00","author":"admin","twitter_card":"summary_large_image","twitter_misc":{"\u4f5c\u8005":"admin","\u9884\u8ba1\u9605\u8bfb\u65f6\u95f4":"8 \u5206"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/www.wsisp.com\/helps\/88882.html","url":"https:\/\/www.wsisp.com\/helps\/88882.html","name":"ConcurrentHashMap \u6df1\u5ea6\u89e3\u6790\uff1a\u4ece\u5206\u6bb5\u9501\u5230 CAS \u7684\u8fdb\u5316\u4e4b\u8def - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","isPartOf":{"@id":"https:\/\/www.wsisp.com\/helps\/#website"},"datePublished":"2026-08-01T13:40:31+00:00","dateModified":"2026-08-01T13:40:31+00:00","author":{"@id":"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41"},"breadcrumb":{"@id":"https:\/\/www.wsisp.com\/helps\/88882.html#breadcrumb"},"inLanguage":"zh-Hans","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.wsisp.com\/helps\/88882.html"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/www.wsisp.com\/helps\/88882.html#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"\u9996\u9875","item":"https:\/\/www.wsisp.com\/helps"},{"@type":"ListItem","position":2,"name":"ConcurrentHashMap \u6df1\u5ea6\u89e3\u6790\uff1a\u4ece\u5206\u6bb5\u9501\u5230 CAS \u7684\u8fdb\u5316\u4e4b\u8def"}]},{"@type":"WebSite","@id":"https:\/\/www.wsisp.com\/helps\/#website","url":"https:\/\/www.wsisp.com\/helps\/","name":"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","description":"\u9999\u6e2f\u670d\u52a1\u5668_\u9999\u6e2f\u4e91\u670d\u52a1\u5668\u8d44\u8baf_\u670d\u52a1\u5668\u5e2e\u52a9\u6587\u6863_\u670d\u52a1\u5668\u6559\u7a0b","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.wsisp.com\/helps\/?s={search_term_string}"},"query-input":"required name=search_term_string"}],"inLanguage":"zh-Hans"},{"@type":"Person","@id":"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41","name":"admin","image":{"@type":"ImageObject","inLanguage":"zh-Hans","@id":"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/image\/","url":"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery","contentUrl":"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery","caption":"admin"},"sameAs":["http:\/\/wp.wsisp.com"],"url":"https:\/\/www.wsisp.com\/helps\/author\/admin"}]}},"_links":{"self":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/posts\/88882","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/comments?post=88882"}],"version-history":[{"count":0,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/posts\/88882\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/media?parent=88882"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/categories?post=88882"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/tags?post=88882"},{"taxonomy":"topic","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/topic?post=88882"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} | |