List集合根据存储对象的属性字段排序实现
public class ListSort {
public static void main(String[] args) {
List students = new ArrayList();
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());
}
}
}
public class Student implements Comparable {
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;
}
}
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
实体类
@AllArgsConstructor
@NoArgsConstructor
@Data
class Teacher {
private String name;
private Integer age;
}
使用Lambda表达式
List teachers = new ArrayList();
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 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;
public class ListSortJava8 {
public static void main(String[] args) {
List teachers = new ArrayList();
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 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;
}