java：带有 lambda 表达式的 Arrays.sort()
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java: Arrays.sort() with lambda expression
提问by matt-pielat
I want to sort String elements in the array monthsby length using Arrays.sortmethod. I was told here, that it's possible to use lambda expressions instead of creating new class implementing Comparator. Did it exactly the same way, yet it doesn't work.
我想months使用Arrays.sort方法按长度对数组中的字符串元素进行排序。有人告诉我，在这里，它是可以使用的，而不是创建新类实现比较lambda表达式。以完全相同的方式做了，但它不起作用。
import java.util.Arrays;
import java.util.Comparator;
public class MainClass {
public static void main(String[] args)
{
String[] months = {"January","February","March","April","May","June","July","August","September","October","December"};
System.out.println(Arrays.toString(months)); //printing before
//neither this works:
Arrays.sort(months,
(a, b) -> Integer.signum(a.length() - b.length())
);
//nor this:
Arrays.sort(months,
(String a, String b) -> { return Integer.signum(a.length() - b.length()) };
);
System.out.println(Arrays.toString(months)); //printing after
}
}
采纳答案by assylias
The cleanest way would be:
最干净的方法是：
Arrays.sort(months, Comparator.comparingInt(String::length));
or, with a static import:
或者，使用静态导入：
Arrays.sort(months, comparingInt(String::length));
However, this would work too but is more verbose:
但是，这也可以工作，但更冗长：
Arrays.sort(months,
(String a, String b) -> a.length() - b.length());
Or shorter:
或更短：
Arrays.sort(months, (a, b) -> a.length() - b.length());
Finally your last one:
最后你的最后一个：
Arrays.sort(months,
(String a, String b) -> { return Integer.signum(a.length() - b.length()) };
);
has the ;misplaced - it should be:
有;错位的-它应该是：
Arrays.sort(months,
(String a, String b) -> { return Integer.signum(a.length() - b.length()); }
);
回答by Josh M
You're looking for this:
你正在寻找这个：
Arrays.sort(months, (a, b) -> Integer.signum(a.length() - b.length()));
回答by Tim B
The functionality you are looking for is in Java 8, which has not yet been released. It is scheduled for release in a few months if you want to wait, or if not beta downloads are available.
您正在寻找的功能在尚未发布的 Java 8 中。如果您想等待，或者没有测试版下载，它计划在几个月内发布。
