Java Collections.sort方法對list集合排序

一、排序測試類

package com.ljq.test;

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

public class UserSort {

    public static void main(String[] args) {
        List<User> userList =new ArrayList<User>();
        userList.add(new User(1,2.2));
        userList.add(new User(2,1.1));
        userList.add(new User(3,4.4));
        userList.add(new User(4,5.5));
        userList.add(new User(5,3.3));
        
        Collections.sort(userList, new Comparator<User>() {
            public int compare(User u1, User u2) {
                return new Double(u1.getSalary()).compareTo(new Double(u2.getSalary())); //升序
                // return new Double(u2.getSalary()).compareTo(new Double(u2.getSalary())); //降序
            }
        });
        
        for(User user : userList){
            System.out.println(user);
        }
    }
}

 

二、User對象，存儲javabean屬性

package com.ljq.test;

import java.io.Serializable;

/**
 * 用戶
 *
 * @author jqlin
 */
public class User implements Serializable{
    private static final long serialVersionUID = 1L;
    
    private long id; // 主鍵
    private double salary; // 薪資

    public User() {

    }

    public User(long id, double salary) {
        super();
        this.id = id;
        this.salary = salary;
    }

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    @Override
    public String toString() {
        return "User [id=" + id + ", salary=" + salary + "]";
    }

}

三、多字段排序，基本數字類型要用封裝數字類型才能夠排序，如：new Double()

        Collections.sort(dataList, new Comparator<OrderVO>(){
            public int compare(OrderVO a, OrderVO b) {
                //先定期號降序，若是期號相同按玩法名稱降序，若是玩法名稱相同按投注時間降序
                int result = b.getCreateTime().compareTo(a.getCreateTime());
                if(result == Zero.INT){
                    return new Integer(a.getSort()).compareTo(new Integer(b.getSort()));
                }else{
                    return result;
                }
            }
        });