1 final Node<K,V>[] resize() { 2 Node<K,V>[] oldTab = table; 3 int oldCap = (oldTab == null) ? 0 : oldTab.length; 4 int oldThr = threshold; 5 int newCap, newThr = 0; 6 if (oldCap > 0) { 7 if (oldCap >= MAXIMUM_CAPACITY) { 8 threshold = Integer.MAX_VALUE; 9 return oldTab; 10 } 11 else if ((newCap = oldCap << 1) < MAXIMUM_CAPACITY && 12 oldCap >= DEFAULT_INITIAL_CAPACITY) //注释1 13 newThr = oldThr << 1; // double threshold 14 } 15 else if (oldThr > 0) // initial capacity was placed in threshold 16 newCap = oldThr; 17 else { // zero initial threshold signifies using defaults 18 newCap = DEFAULT_INITIAL_CAPACITY; 19 newThr = (int)(DEFAULT_LOAD_FACTOR * DEFAULT_INITIAL_CAPACITY); 20 } 21 if (newThr == 0) { 22 float ft = (float)newCap * loadFactor; 23 newThr = (newCap < MAXIMUM_CAPACITY && ft < (float)MAXIMUM_CAPACITY ? 24 (int)ft : Integer.MAX_VALUE); 25 } 26 threshold = newThr; 27 @SuppressWarnings({"rawtypes","unchecked"}) 28 Node<K,V>[] newTab = (Node<K,V>[])new Node[newCap]; 29 table = newTab; 30 if (oldTab != null) { 31 for (int j = 0; j < oldCap; ++j) { //注释2 32 Node<K,V> e; 33 if ((e = oldTab[j]) != null) {//注释3 34 oldTab[j] = null; 35 if (e.next == null) //注释4 36 newTab[e.hash & (newCap - 1)] = e; 37 else if (e instanceof TreeNode) //注释5 38 ((TreeNode<K,V>)e).split(this, newTab, j, oldCap); 39 else { // preserve order //注释6 40 Node<K,V> loHead = null, loTail = null; //注释7 41 Node<K,V> hiHead = null, hiTail = null;//注释8 42 Node<K,V> next; 43 do { 44 next = e.next; 45 if ((e.hash & oldCap) == 0) { //注释9 46 if (loTail == null) //注释10 47 loHead = e; 48 else 49 loTail.next = e; 50 loTail = e; 51 } 52 else { 53 if (hiTail == null)//注释11 54 hiHead = e; 55 else 56 hiTail.next = e; 57 hiTail = e; 58 } 59 } while ((e = next) != null); 60 if (loTail != null) { //注释12 61 loTail.next = null; 62 newTab[j] = loHead; 63 } 64 if (hiTail != null) {//注释13 65 hiTail.next = null; 66 newTab[j + oldCap] = hiHead; 67 } 68 } 69 } 70 } 71 } 72 return newTab; 73 }注释1:对新横向node数组的长度和容量阀值均扩容为2倍 注释2:遍历旧横向node数组中每个node节点,在后面的代码中对每个node节点重新分配下标位置到新横向node数组 注释3:旧横向node数组中当前节点为空,则跳过 注释4:旧横向node数组中当前节点若只有一个元素(构不成node链表、红黑树),则直接给该node节点分配下标位置到新横向node数组 注释5:旧横向node数组中当前节点是红黑树节点,则直接调用红黑树的split()方法对红黑树进行修剪 注释6:旧横向node数组中当前节点是普通链表头节点,则为该链表重新分配下标到新横向node数组 注释7:旧横向node数组中当前节点下标=重新分配的新横向node数组中当前节点下标,则用loHead 表示旧横向node数组中当前node节点(即链表头),用loTail 表示旧横向node数组中当前node节点的链表尾 注释8:与注释7相反,旧横向node数组中当前节点下标 不等于 重新分配的新横向node数组中当前节点下标,hiHead表示新横向node数组的链表头节点,hiTail 表示新横向node数组的链表尾节点 注释9:重点,见下图。当“hash值”和“容量”进行与操作时,若结果为0,则当前节点在新旧横向node数组下标相等;否则若结果不为0,则当前节点在新横向node数组下标=该节点在旧横向的下标+旧容量(即旧横向node数组的长度) 注释10:当前节点在新旧横向node数组下标相等,用loTail 、loHead 标识 注释11:当前节点在新旧横向node数组下标不相等,用hiTail、hiHead 标识 注释12:loTail不为空,代表当前节点在新旧横向node数组下标相等 注释13:hiTail 不为空,代表当前节点在新旧横向node数组下标不相等,即当前节点在新横向node数组下标=旧横向的下标+旧容量