Java中如何给List进行排序(这7种方法轻松实现)

package com.test.javaroads.java8sort;
import lombok.Data;
/**
 * @author: javaroads
 * @date: 2022/11/22 22:06
 * @description: 学生类
 */
@Data
@AllArgsConstructor
public class Student {
    /**
     * 学生ID
     */
    private String sid;
    /**
     * 学生姓名
     */
    private String name;
    /**
     * 学生年龄
     */
    private Integer age;
    /**
     * 性别
     */
    private String gender;
    /**
     * 所属班级
     */
    private String className;
}

package com.test.javaroads.java8sort;

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

/**
 * @author: javaroads
 * @date: 2022/11/22 22:12
 * @description: 排序方法
 */
public class Sort {

    public static void main(String[] args) {
        List<Student> studentList = Arrays.asList(
                new Student("s1", "小李", 18, "女", "一班"),
                new Student("s2", "小王", 20, "男", "三班"),
                new Student("s3", "小张", 19, "男", "四班"),
                new Student("s4", "小汪", 19, "男", "二班"));

        System.out.println("排序前");
        studentList.forEach(System.out::println);

        // 方法一：Java8之前，不用lambda表达式
        Collections.sort(studentList, new Comparator<Student>() {
            @Override
            public int compare(Student student1, Student student2) {
                return student1.getAge() - student2.getAge();
            }
        });

        // 用forEach打印出排序后的list
        System.out.println("排序后的list：");
        studentList.forEach(System.out::println);
    }
}

// 方法二：Java8中使用lambda表达式
Collections.sort(studentList, (student1, student2) -> student1.getClassName().compareTo(student2.getClassName()));

// 方法三：通过类型推断增强lambda表达式
Collections.sort(studentList, (student1, student2) -> student1.getAge() - student2.getAge());

/**
 * 根据年龄对学生进行排序
 *
 * @param student1 学生1
 * @param student2 学生2
 * @return 数字
 */
public static int compareByAge(Student student1, Student student2) {
    return student1.getAge().compareTo(student2.getAge());
}

// 方法四：通过lambda表达式结合静态方法引用
Collections.sort(studentList, Student::compareByAge);

// 方法五：通过使用Comaprator的comparing()方法
Collections.sort(studentList, Comparator.comparing(Student::getAge));

// 方法六：lambda倒叙
Comparator<Student> compare = (student1, student2) -> student1.getAge() - student2.getAge();
Collections.sort(studentList, compare.reversed());

// 方法七：多条件排序
Collections.sort(studentList, (student1, student2) -> {
    if (student1.getGender().equals(student2.getGender())) {
        return student1.getAge() - student2.getAge();
    } else {
        return student1.getClassName().compareTo(student2.getClassName());
    }
});