那么HashMap什么时候进行扩容呢？

          //HashMap数组扩容
          void resize(int newCapacity) {
                Entry[] oldTable = table;
                int oldCapacity = oldTable.length;
                //如果当前的数组长度已经达到最大值，则不再进行调整
                if (oldCapacity == MAXIMUM_CAPACITY) {
                    threshold = Integer.MAX_VALUE;
                    return;
                }
                //根据传入参数的长度定义新的数组
                Entry[] newTable = new Entry[newCapacity];
                //按照新的规则，将旧数组中的元素转移到新数组中
                transfer(newTable);
                table = newTable;
                //更新临界值
                threshold = (int)(newCapacity * loadFactor);
            }

          //旧数组中元素往新数组中迁移
            void transfer(Entry[] newTable) {
                //旧数组
                Entry[] src = table;
                //新数组长度
                int newCapacity = newTable.length;
                //遍历旧数组
                for (int j = 0; j < src.length; j++) {
                    Entry<K,V> e = src[j];
                    if (e != null) {
                        src[j] = null;
                        do {
                            Entry<K,V> next = e.next;
                            int i = indexFor(e.hash, newCapacity);
                            e.next = newTable[i];
                            newTable[i] = e;
                            e = next;
                        } while (e != null);
                    }
                }
            }