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 {

    @Test

    public void test1(){

        /**

         * Collections.sort()使用

         */

        //被排序的集合

        List<User> 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<User>() {

            @Override

            public 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User

        userList.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<User> 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));

    }

}