Java Streams .max()和.min()在性能上滞后吗?

问题描述

考虑以下2个示例.

myList.stream().map(this::getInt).max(Integer::compareTo);

2旧方式

int max = Integer.MIN_VALUE;
for (MyItem item : myList) {
    max = Math.max(max, getInt(item));    
}

getInt以上的方法接受MyItem自变量并返回int结果.

Above getInt method accepts a MyItem argument and returns an int result.

在这里，与#1相比，#2给我的等待时间要短得多.有谁知道为什么或者我有什么问题吗?

Here, #2 gives me a much lower latency compared to #1. Does anyone have an idea why or anything going wrong for me?

推荐答案

myList.stream().mapToInt(this::getInt).max()

尝试映射到IntStream . IntStream在内部与int一起使用，这避免了对Integer对象进行装箱和拆箱的开销.另外， IntStream.max() 不需要自定义比较器.

Try mapping to an IntStream. An IntStream works with ints internally, which avoids the overhead of boxing and unboxing Integer objects. Also, IntStream.max() doesn't need a custom comparator.

如果没有通过基准测试运行它，我不知道它是否会符合for循环的性能.但这将是一个进步.如果还不够好，那么我建议您坚持使用循环，因为我看不到任何其他改进方法.

Without running it through your benchmark I don't know if it'll match the for loop's performance. But it'll be an improvement. If it's not good enough then I suggest sticking with the loop as I don't see any other way to improve it.

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