List集合根据存储对象的属性字段排序实现

1. List集合根据存储对象的属性字段排序实现

package com.huixin;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/**
 * ListSort类
 *
 * @author Lance
 * @date 2017/03/10
 */
public class ListSort {
public static void main(String[] args) {
        List<Student> students = new ArrayList<Student>();
        students.add(new Student("张三", 24));
        students.add(new Student("李四", 23));
        students.add(new Student("王五", 25));
        System.out.println("before sort:");
for (Student bean : students) {
            System.out.println("before sort---->age: " + bean.getAge());
        }
        Collections.sort(students);
        System.out.println("after sort:");
for (Student bean : students) {
            System.out.println("after sort---->age: " + bean.getAge());
        }
    }
}
class Student implements Comparable<Student> {
private String name;
private Integer age;
public Student(String name, Integer age) {
this.name = name;
this.age = age;
    }

/*
 * s的age小于this的对应字段，则返回负数；
 * 大于则返回正数；
 * 建议去了解compareTo背后的真相
 */
@Override
public int compareTo(Student s) {
return s.getAge().compareTo(this.getAge());
    }

public Integer getAge() {
return age;
    }

public void setAge(Integer age) {
this.age = age;
    }

public String getName() {
return name;
    }

public void setName(String name) {
this.name = name;
    }
}

1. 预期结果

Connected to the target VM, address: '127.0.0.1:3850', transport: 'socket'
before sort:
before sort---->age: 24
before sort---->age: 23
before sort---->age: 25
after sort:
after sort---->age: 25
after sort---->age: 24
after sort---->age: 23

======================================================
以上是java8之前的用法，java8提供了多种操作方式。博文修改2017.4.7

• 实体类

@AllArgsConstructor
@NoArgsConstructor
@Data
class Teacher {
private String name;
private Integer age;
}

• 使用Lambda表达式

 List<Teacher> teachers = new ArrayList<Teacher>();
        teachers.add(new Teacher("张三", 24));
        teachers.add(new Teacher("李四", 23));
        teachers.add(new Teacher("王五", 25));
        System.out.println("before sort:");
for (Teacher bean : teachers) {
            System.out.println("before sort---->age: " + bean.getAge());
        }
//Lambda
        teachers.sort((s1, s2) -> s1.getAge().compareTo(s2.getAge()));
System.out.println("after sort:");
for (Teacher bean : teachers) {
System.out.println("after sort---->age: " + bean.getAge());
 }

• 使用Comparator操作器

//Comparator
        Collections.sort(teachers, Comparator.comparing(Teacher::getAge));

• 反序排列

Comparator<Teacher> comparator = (t1, t2) -> t1.getAge().compareTo(t2.getAge());
        teachers.sort(comparator.reversed());

• 组合排序

//组合排序
        teachers.sort(Comparator.comparing(Teacher::getAge).thenComparing(Teacher::getName));

• 完整示例代码

package com.huixin.utils.common;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * ListSort类
 *
 * @author Lance
 * @date 2017/03/10
 */
public class ListSortJava8 {
public static void main(String[] args) {
        List<Teacher> teachers = new ArrayList<Teacher>();
        teachers.add(new Teacher("张三", 24));
        teachers.add(new Teacher("李四", 23));
        teachers.add(new Teacher("王五", 25));
        teachers.add(new Teacher("钱二", 23));
        System.out.println("before sort:");
for (Teacher bean : teachers) {
            System.out.println("before sort---->age: " + bean.getAge() + "==name：" + bean.getName());
        }
//Lambda
// teachers.sort((t1, t2) -> s1.getAge().compareTo(s2.getAge()));
//Comparator
// Collections.sort(teachers, Comparator.comparing(Teacher::getAge));
//reversed
// Comparator<Teacher> comparator = (t1, t2) -> t1.getAge().compareTo(t2.getAge());
// teachers.sort(comparator.reversed());
//组合排序
        teachers.sort(Comparator.comparing(Teacher::getAge).thenComparing(Teacher::getName));
        System.out.println("after sort:");
for (Teacher bean : teachers) {
            System.out.println("after sort---->age: " + bean.getAge() + "==name：" + bean.getName());
        }
    }
}

@AllArgsConstructor
@NoArgsConstructor
@Data
class Teacher {
private String name;
private Integer age;
}