hashmap

if ((e = p.next) == null) {

p.next = newNode(hash, key, value, null);
if (binCount >= TREEIFY_THRESHOLD - 1) // -1 for 1st
    treeifyBin(tab, hash);
break;

}
(e = p.next) == null 为true
p.next = newNode(hash, key, value, null);
e==null
so,覆盖不会增加size,链表追加会增加size导致扩容