08 arrayList扩容时扩容多少

//默认容量大小
private static final int DEFAULT_CAPACITY = 10;

//扩容 当前数据长度+1 作为最小容量
public boolean add(E e) {
    ensureCapacityInternal(size + 1);  // Increments modCount!!
    elementData[size++] = e;
    return true;
}
private void ensureCapacityInternal(int minCapacity) {
    ensureExplicitCapacity(calculateCapacity(elementData, minCapacity));
}
// 计算容量 如果原始为空数组，则取默认容量10和+1后的容量 取二者大的
private static int calculateCapacity(Object[] elementData, int minCapacity) {
    // 如果为空则返回默认容量的空数组对象
    if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) {
        return Math.max(DEFAULT_CAPACITY, minCapacity);
    }
    // 否则返回+1后容量
    return minCapacity;
}
// 计算显示容量 最小容量大于当前数据长度 表示需要扩容了
// 即如果当前数据长度+1大于10 则扩容
private void ensureExplicitCapacity(int minCapacity) {
    modCount++;

    // overflow-conscious code
    if (minCapacity - elementData.length > 0)
        grow(minCapacity);
}
//扩容右位移1位  10>>1 为5扩容后是15  扩容为之前的1.5倍
//最大为MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8
//public static final int   MAX_VALUE = 2^31-1;
private void grow(int minCapacity) {
    // overflow-conscious code
    int oldCapacity = elementData.length;
    int newCapacity = oldCapacity + (oldCapacity >> 1);
    if (newCapacity - minCapacity < 0)
        newCapacity = minCapacity;
    if (newCapacity - MAX_ARRAY_SIZE > 0)
        newCapacity = hugeCapacity(minCapacity);
    // minCapacity is usually close to size, so this is a win:
    elementData = Arrays.copyOf(elementData, newCapacity);
}
private static int hugeCapacity(int minCapacity) {
    if (minCapacity < 0) // overflow
        throw new OutOfMemoryError();
    return (minCapacity > MAX_ARRAY_SIZE) ?
        Integer.MAX_VALUE :
        MAX_ARRAY_SIZE;
}