ArrayList

         1、ArrayList源码

                 1、add方法  先扩容，后赋值

    //添加方法
    public boolean add(E e) {
        //将数组扩容，
        ensureCapacityInternal(size + 1);
        //将原数组+1的位置 赋值
        elementData[size++] = e;
        return true;
    }

                2、扩容方法

    private void ensureExplicitCapacity(int minCapacity) {
        //操作次数+1
        modCount++;
      
        // overflow-conscious code
        if (minCapacity - elementData.length > 0)
            grow(minCapacity);
    }

    //扩容
    private void grow(int minCapacity) {
        int oldCapacity = elementData.length;
        //原有数组长度右移一位  比如10  就是 10 + 5
        int newCapacity = oldCapacity + (oldCapacity >> 1);
        if (newCapacity - minCapacity < 0)
            newCapacity = minCapacity;
        if (newCapacity - MAX_ARRAY_SIZE > 0)
            newCapacity = hugeCapacity(minCapacity);
        // 重新创建到一个新长度的数组
        elementData = Arrays.copyOf(elementData, newCapacity);
    }

标签：右移,初始化,int,ArrayList,elementData,newCapacity,minCapacity,数组,oldCapacity
来源： https://blog.csdn.net/qq_38384460/article/details/112920555