1.在看Vector源码是有2个小知识点比较疑惑
2.疑惑代码如下
/**
This implements the unsynchronized semantics of ensureCapacity.
Synchronized methods in this class can internally call this
method for ensuring capacity without incurring the cost of an
extra synchronization.
*
@see #ensureCapacity(int)
*/
void ensureCapacityHelper(int minCapacity) {
1
551 // overflow-conscious code
if (minCapacity - elementData.length > 0)
grow(minCapacity);}
/**
The maximum size of array to allocate.
Some VMs reserve some header words in an array.
Attempts to allocate larger arrays may result in
OutOfMemoryError: Requested array size exceeds VM limit
*/
static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
3.疑惑问题点如下：
问题点1：if (minCapacity - elementData.length > 0)，为啥不这样写
if(minCapacity>elementData.length),效率高在哪？
问题点2：MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;为啥是减8而不是其他，注释没看明白是啥意思
Copyright 2014-2026 https://www.php.cn/ All Rights Reserved | php.cn | 湘ICP备2023035733号
收藏
拥有18年软件开发和IT教学经验。曾任多家上市公司技术总监、架构师、项目经理、高级软件工程师等职务。 网络人气名人讲师，...