Java8 Collections.sort()及Arrays.sort()中Lambda表达式及增强版Comparator的使用

摘要：本文主要介绍Java8 中Arrays.sort()及Collections.sort()中Lambda表达式及增强版Comparator的使用。

不废话直接上代码

import com.google.common.collect.Lists;
import org.junit.Assert;
import org.junit.Test;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;public class ComparatorTest {@Testpublic void test1(){/*** Collections.sort()使用*///被排序的集合List userList = Lists.newArrayList(new User("Jack",11),new User("Jack",10));//1. Java8之前，使用匿名内部类的基本排序Collections.sort(userList, new Comparator() {@Overridepublic int compare(User user1, User user2) {return user1.getAge().compareTo(user2.getAge());}});//2. Java8,使用Lambda表达式的基本排序
        Collections.sort(userList,(User user1, User user2) ->user1.getAge().compareTo(user2.getAge()));//userList.sort((User user1, User user2) -> user1.getAge().compareTo(user2.getAge()));//3. Java8,Lambda表达式可以简化，省略定义类型UseruserList.sort((user1, user2) -> user1.getAge().compareTo(user2.getAge()));//4. Java8,Lambda表达式，多条件排序userList.sort((user1, user2) -> {if (user1.getName().equals(user2.getName())) {return user1.getAge() - user2.getAge();} else {return user1.getName().compareTo(user2.getName());}});//5. Java8,多条件组合排序
        userList.sort(Comparator.comparing(User::getName).thenComparing(User::getAge));//6. Java8,提取Comparator进行排序
        Collections.sort(userList, Comparator.comparing(User::getName));//7. Java8,自定义静态的比较方法来排序(静态方法必须写在被比较的类(这里是User类)中)
        userList.sort(User::compareByAgeThenName);//8. Java8,反转排序Comparator comparator = (user1, user2) -> user1.getName().compareTo(user2.getName());userList.sort(comparator);//先按name排序userList.sort(comparator.reversed());//反转排序Assert.assertEquals(userList.get(0),new User("Jack",10));/*** Arrays.sort()使用*///被排序的字符串数组String[] months = {"January","February","March","April","May","June","July","August","September","October","December"};//按字符串长度排序//1.Arrays.sort(months, (a, b) -> Integer.signum(a.length() - b.length()));//2.
        Arrays.sort(months, Comparator.comparingInt(String::length));//3.Arrays.sort(months, (a, b) -> a.length() - b.length());//4.
        Arrays.sort(months,(String a, String b) -> { return Integer.signum(a.length() - b.length()); });System.out.println(Arrays.toString(months));}
}

原文地址：https://blog.csdn.net/qq_27127145/article/details/83930498

转载于:https://www.cnblogs.com/huiyi0521/p/10990535.html

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