java源碼一帶一路系列之HashMap.compute()

@Override public V compute(K key, BiFunction remappingFunction) { if (remappingFunction == null) throw new NullPointerException; int hash = hash(key); Node tab; Node first; int n, i; int binCount = 0; TreeNode t = null; Node old = null; if (size > threshold || (tab = table) == null || (n = tab.length) == 0) n = (tab = resize).length; if ((first = tab[i = (n - 1) & hash]) != null) { if (first instanceof TreeNode) old = (t = (TreeNode)first).getTreeNode(hash, key); else { Node e = first; K k; do { if (e.hash == hash && ((k = e.key) == key || (key != null && key.equals(k)))) { old = e; break; } ++binCount; } while ((e = e.next) != null); } } V oldValue = (old == null) ? null : old.value; V v = remappingFunction.apply(key, oldValue); if (old != null) { if (v != null) { old.value = v; afterNodeAccess(old); } else removeNode(hash, key, null, false, true); } else if (v != null) { if (t != null) t.putTreeVal(this, tab, hash, key, v); else { tab[i] = newNode(hash, key, v, first); if (binCount >= TREEIFY_THRESHOLD - 1) treeifyBin(tab, hash); } ++modCount; ++size; afterNodeInsertion(true); } return v; }

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