java lambda List 排序 sorted-526互联

package lambda.list;

import lombok.extern.slf4j.Slf4j;
import org.junit.Test;
import pojo.Dome;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;

/**
 * @Author: xxx
 * @date 2021/5/14
 **/
@Slf4j
public class SortTest {

    /***
     * 初始化测试数组
     * @date 2021/5/14
     **/

    private List<Dome> initArray() {
        Dome dome1 = new Dome("张三", 11.0, 10);
        Dome dome2 = new Dome("李四", 61.0, 11);
        Dome dome3 = new Dome("王五", 26.0, 12);
        Dome dome4 = new Dome("张三", 14.0, 14);
        Dome dome5 = new Dome("王五", 24.0, 15);
        Dome dome6 = new Dome("李四", 16.0, 16);
        Dome dome7 = new Dome("赵六", 35.0, 17);

        List<Dome> domes = new ArrayList<>();

        domes.add(dome1);
        domes.add(dome2);
        domes.add(dome3);
        domes.add(dome4);
        domes.add(dome5);
        domes.add(dome6);
        domes.add(dome7);

        log.info("domes : {}", domes);

        return domes;
    }

    /***
     * List 排序正序
     * @date 2021/5/13
     **/

    @Test
    public void sortTest1() {
        List<Dome> domes = initArray();
        List<Dome> collect = domes.stream().sorted((s1, s2) -> s1.getMoney().compareTo(s2.getMoney())).collect(Collectors.toList());
        log.info("collect : {}", collect);

        domes.sort((s1, s2) -> s2.getMoney().compareTo(s1.getMoney()));
        log.info("domes : {}", domes);

/*
domes : [Dome{name='张三', money=11.0, age=10}, Dome{name='李四', money=61.0, age=11}, Dome{name='王五', money=26.0, age=12}, Dome{name='张三', money=14.0, age=14}, Dome{name='王五', money=24.0, age=15}, Dome{name='李四', money=16.0, age=16}, Dome{name='赵六', money=35.0, age=17}]
collect : [Dome{name='张三', money=11.0, age=10}, Dome{name='张三', money=14.0, age=14}, Dome{name='李四', money=16.0, age=16}, Dome{name='王五', money=24.0, age=15}, Dome{name='王五', money=26.0, age=12}, Dome{name='赵六', money=35.0, age=17}, Dome{name='李四', money=61.0, age=11}]
domes : [Dome{name='李四', money=61.0, age=11}, Dome{name='赵六', money=35.0, age=17}, Dome{name='王五', money=26.0, age=12}, Dome{name='王五', money=24.0, age=15}, Dome{name='李四', money=16.0, age=16}, Dome{name='张三', money=14.0, age=14}, Dome{name='张三', money=11.0, age=10}]
*/
    }

    /***
     * List 排序倒序
     * @date 2021/5/13
     **/

    @Test
    public void sortTest2() {
        List<Dome> domes = initArray();
        List<Dome> collect = domes.stream().sorted(Comparator.comparing(Dome::getMoney).reversed()).collect(Collectors.toList());
        log.info("collect : {}", collect);
/*
domes : [Dome{name='张三', money=11.0, age=10}, Dome{name='李四', money=61.0, age=11}, Dome{name='王五', money=26.0, age=12}, Dome{name='张三', money=14.0, age=14}, Dome{name='王五', money=24.0, age=15}, Dome{name='李四', money=16.0, age=16}, Dome{name='赵六', money=35.0, age=17}]
collect : [Dome{name='李四', money=61.0, age=11}, Dome{name='赵六', money=35.0, age=17}, Dome{name='王五', money=26.0, age=12}, Dome{name='王五', money=24.0, age=15}, Dome{name='李四', money=16.0, age=16}, Dome{name='张三', money=14.0, age=14}, Dome{name='张三', money=11.0, age=10}]
*/
    }

    /**
     * 对二维数组{x,y}的y进行从小到大排序
     *
     *  方法1：
     *  重写比较器写法
     */

    @Test
    public void sortTest3() {
        int[][] nums = {{3, 1}, {4, 2}};
        Arrays.sort(nums,new Comparator<int[]>(){
            @Override
            public int compare(int[] a,int[] b){
                if(a[1]==b[1]){
                    return a[0]-b[0];
                }else{
                    return a[1]-b[1];
                }
            }
        });
        for (int i = 0; i < nums.length; i++) {
            for (int j = 0; j < nums[0].length; j++) {
                System.out.print(nums[i][j]+" ");
            }
            System.out.println();
        }
    }

    /**
     * 对二维数组{x,y}的y进行从小到大排序
     *
     *  方法2：
     *  Lambda表达式写法
     */
    @Test
    public void sortTest4(){
        int[][] nums = {{3, 1}, {4, 2}};
        /*Arrays.sort(nums, (a, b) -> {
            return a[1] == b[1] ? a[0] - b[0] : a[1] - b[1];
        });*/
        Arrays.sort(nums, (a, b) -> a[1] == b[1] ? a[0] - b[0] : a[1] - b[1]);
        for (int i = 0; i < nums.length; i++) {
            for (int j = 0; j < nums[0].length; j++) {
                System.out.print(nums[i][j]+" ");
            }
            System.out.println();
        }
    }

    /**
     * 对二维数组{x,y}的y进行从小到大排序
     *
     *  方法3：
     *  更简洁的Lambda表达式
     */
    @Test
    public void sortTest5(){
        int[][] nums = {{3, 1}, {4, 0}, {8, 5}, {9, -8}};
        /* Arrays.sort(nums, (o1, o2) -> o1[1] - o2[1]); */
        Arrays.sort(nums, Comparator.comparingInt(o -> o[1]));
        for (int i = 0; i < nums.length; i++) {
            for (int j = 0; j < nums[0].length; j++) {
                System.out.print(nums[i][j]+" ");
            }
            System.out.println();
        }
    }

    /**
     * 多字段排序 优化
     */
    @Test
    public void sortTest6(){
        List<Dome> domes = initArray();
        //单字段排序，根据id排序
        domes.sort(Comparator.comparing(Dome::getAge));
        //多字段排序，根据id，年龄排序
        domes.sort(Comparator.comparing(Dome::getAge).thenComparing(Dome::getMoney));

        //普通的排序取值
        List<Dome> list11 = domes.stream().sorted((u1, u2) -> u1.getMoney().compareTo(u2.getMoney())).limit(3).collect(Collectors.toList());
        System.out.println("排序之后的数据:" + list11);
        //优化排序取值
        List<Dome> list12 = domes.stream().limit(3).sorted((u1, u2) -> u1.getMoney().compareTo(u2.getMoney())).collect(Collectors.toList());
        System.out.println("优化排序之后的数据:" + list12);
        //排序之后的数据:[{"id":1,"name":"pancm1"}, {"id":2,"name":"pancm2"}, {"id":3,"name":"pancm3"}]
        //优化排序之后的数据:[{"id":1,"name":"pancm1"}, {"id":2,"name":"pancm2"}, {"id":3,"name":"pancm3"}]

    }

}