关于Java的ArrayList数组自动扩容机制

private void grow(int minCapacity) {
    // overflow-conscious code
    int oldCapacity = elementData.length;
    // jdk1.7采用位运算比以前的计算方式更快
    int newCapacity = oldCapacity + (oldCapacity >> 1);
    if (newCapacity - minCapacity < 0)
        newCapacity = minCapacity;
    //jdk1.7这里增加了对元素个数的最大个数判断，MAX_ARRAY_SIZE 为int最大值减去8。
    if (newCapacity - MAX_ARRAY_SIZE > 0)
        newCapacity = hugeCapacity(minCapacity);
    // minCapacity is usually close to size, so this is a win:
    // 最重要的复制元素方法   Arrays.copyOf() 
    elementData = Arrays.copyOf(elementData, newCapacity);
}