Java源码 HashMap.roundUpToPowerOf2原理

int rounded = number >= MAXIMUM_CAPACITY ? MAXIMUM_CAPACITY

 : (rounded = Integer.highestOneBit(number)) != 0 ?

 (Integer.bitCount(number) > 1) ? rounded << 1 : rounded

                                        : 1;

分析rounded求解过程：

Created with Raphaël 2.1.0开始number >= 2^302^30返回rounded = Integer.highestOneBit(number)rounded !=0 Integer.bitCount(number) > 1rounded << 1 rounded1yesnoyesnoyesno

流程图

Created with Raphaël 2.1.0开始number >= 2^302^30返回rounded，求最接近的r=2^nrounded !=0 number >rnumber>r 则两倍之本来就是2^n的值得round1yesnoyesnoyesno

流程图分析