/**
* Implements Map.put and related methods
*
* @param hash hash for key
* @param key the key
* @param value the value to put
* @param onlyIfAbsent if true, don't change existing value
* @param evict if false, the table is in creation mode.
* @return previous value, or null if none
*/
final V putVal(int hash, K key, V value, boolean onlyIfAbsent,
boolean evict) {
Node<K,V>[] tab; Node<K,V> p; int n, i;
//未初始化就初始化
if ((tab = table) == null || (n = tab.length) == 0)
n = (tab = resize()).length;
//数组中hash对应的索引位置上为null,建立新节点
if ((p = tab[i = (n - 1) & hash]) == null) //取出p
tab[i] = newNode(hash, key, value, null);
//hash对应位置存在对象
else {
Node<K,V> e; K k;
//哈希相等 && (key相等 || key Equal) == 键相等
if (p.hash == hash &&
((k = p.key) == key || (key != null && key.equals(k))))
e = p;
//对应位置是树
else if (p instanceof TreeNode)
e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value);
//对应位置是链表
else {
for (int binCount = 0; ; ++binCount) {
//最后一个了
if ((e = p.next) == null) {
//放到链表尾
p.next = newNode(hash, key, value, null);
//树化
if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
treeifyBin(tab, hash);
break;
}
//哈希相等 && (key相等 || key Equal) == 键相等
if (e.hash == hash &&
((k = e.key) == key || (key != null && key.equals(k))))
break;
p = e;//新节点赋值给p
}
}
if (e != null) { // 键之前就存在
V oldValue = e.value;
if (!onlyIfAbsent || oldValue == null) //旧值为null时将被新值替换
e.value = value;
afterNodeAccess(e);//????
return oldValue;//返回旧值
}
}
++modCount;//修改次数 + 1
if (++size > threshold)//扩容
resize();
afterNodeInsertion(evict);//????
return null;
}
