java--->ArrayList進行排序的實現

package com.cai.test;

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

/**
 * 目標，實現對List進行自定義排序
 */
public class ListSort {
    public static void main(String[] args) {
        method3();

    }
    /**
     * 1.直接Collections進行排序
     */
    public static void method1(){
        List<Integer> listInteger = new ArrayList<Integer>();
        listInteger.add(5);
        listInteger.add(8);
        listInteger.add(1);
        listInteger.add(22);
        Collections.sort(listInteger);
        System.out.println(listInteger.toString());//[1, 5, 8, 22]
    }

    /**
     * 2.進行實體類的排序 ，實體類實現Comparable接口，自定義排序方式
     */
    public static void method2(){
        List<User> userList = new ArrayList<User>();
        userList.add(new User("路飛",19));
        userList.add(new User("香克斯",42));
        userList.add(new User("大媽",50));
        userList.add(new User("黑胡子",39));
        userList.add(new User("凱多",49));
        Collections.sort(userList);
        System.out.println(userList.toString());
        //[User{name='路飛', age=19}, User{name='黑胡子', age=39}, User{name='香克斯', age=42}, User{name='凱多', age=49}, User{name='大媽', age=50}]
    }

    /**
     * Collections中的匿名內部類進行排序
     */
    public static void method3(){
        List<User> userList = new ArrayList<User>();
        userList.add(new User("路飛",19));
        userList.add(new User("香克斯",42));
        userList.add(new User("大媽",50));
        userList.add(new User("黑胡子",39));
        userList.add(new User("凱多",49));
        Collections.sort(userList, new Comparator<User>() {

            @Override
            public int compare(User o1, User o2) {
                //這里 和 放法2 打印區分 這里用年齡降序
                int dif = o1.getAge()-o2.getAge();
                if(dif>0){
                    return -1;
                }else if(dif<0){
                    return 1;
                }
                return 0;
            }
        });
        System.out.println(userList.toString());
        //[User{name='大媽', age=50}, User{name='凱多', age=49}, User{name='香克斯', age=42}, User{name='黑胡子', age=39}, User{name='路飛', age=19}]
    }

}
class User implements Comparable<User>{
    private String name;
    private int age;

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    /**
     * 重寫Comparable接口的compareTo方法，
     * 根據年齡升序排列，降序修改相減順序即可
     * @param
     * @return
     */
    @Override
    public int compareTo(User user) {
        return this.age-user.age;
    }
}