在Java中，将String :: length用作Comparator.comparing() [英] in java, use String::length for Comparator.comparing()

问题描述

我有一个这样的代码段:

I have a code piece like this:

String[] yetToSortedArray = {"Abc","hello world","nihao?","chilemaNin"};
Arrays.parallelSort(yetToSortedArray, Comparator.comparing(String::length));
for(String str : yetToSortedArray){
    System.out.println(str + ", ");
}

我的问题在这里:字符串::长度" 我真正传递给Comparator.comparing()的是什么? 为什么String :: length()没有括号?

My question is here: "String::length" What am I really passing in to Comparator.comparing()? Why there is no parenthesis for String::length()?

我认为我正在使用它:

I think I am using this : https://docs.oracle.com/javase/8/docs/api/java/util/Comparator.html#comparing-java.util.function.Function-java.util.Comparator-

它说:接受一个从类型T中提取一个Comparable排序键，然后返回一个通过该排序键进行比较的Comparator的函数."

And it says "Accepts a function that extracts a Comparable sort key from a type T, and returns a Comparator that compares by that sort key."

String :: length如何匹配此类型?

How dos String::length match this type?

谢谢.

推荐答案

String::length是 方法参考 .使用它等同于

String::length is a method reference. Using it is equivalent to

Comparator.comparing(s -> s.length())

因此它通过比较字符串的长度来比较字符串.

So it compares strings by comparing their length.

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