jdk源码

char[] value;

// 表示字符个数
int count;

// 翻倍，不够取所需最小
private int (int minCapacity) {
    // overflow-conscious code
    int newCapacity = (value.length << 1) + 2;
    if (newCapacity - minCapacity < 0) {
            newCapacity = minCapacity;
    }
    return (newCapacity <= 0 || MAX_ARRAY_SIZE - newCapacity < 0)
        ? hugeCapacity(minCapacity)
        : newCapacity;
}

// 判断
private int hugeCapacity(int minCapacity) {
        if (Integer.MAX_VALUE - minCapacity < 0) { // overflow
            throw new OutOfMemoryError();
        }
        return (minCapacity > MAX_ARRAY_SIZE)
            ? minCapacity : MAX_ARRAY_SIZE;
    }