java - 如何在Java升序中按内部值对对象排序？

Question

我有包含数据的对象列表，如Name（String）和Timestamp（Long）。我试图基于时间戳按升序对这些对象进行排序。

MyCode.java

import java.util.ArrayList;
import java.util.Collections;

class Friend
{
    long time;
    String name;
    Friend(long t,String n)
    {
        time=t;
        name=n;
    }
}


public class Practice4 {
    public static void main(String[] args) {
        long l1=1590065750535l;
        long l2=1590065760674l;
        long l3=1590065784567l;
        long l4=1590065760674l;

        Friend f[]=new Friend[4];

        f[0]=new Friend(l1,"A");
        f[1]=new Friend(l3,"B");
        f[2]=new Friend(l2,"C");
        f[3]=new Friend(l4,"D");

        ArrayList<Friend> list=new ArrayList<Friend>();
        list.add(f[0]); list.add(f[1]); list.add(f[2]); list.add(f[3]);

        Collections.sort(list); //error
        System.out.println(list);
    }
}

如何按时间戳对这些Friend对象排序并显示它们？

Answer 1

此代码解决了问题。

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

class Friend 
{
    long time;
    String name;
    Friend(long t,String n)
    {
        time=t;
        name=n;
    }
}


public class Practice4 {
    public static void main(String[] args) {
        long l1=1590065750535l;
        long l2=1590065760674l;
        long l3=1590065784567l;
        long l4=1590065760674l;

        Friend f[]=new Friend[4];

        f[0]=new Friend(l1,"A");
        f[1]=new Friend(l3,"B");
        f[2]=new Friend(l2,"C");
        f[3]=new Friend(l4,"D");

        ArrayList<Friend> list=new ArrayList<Friend>();
        for(int i=0;i<f.length;i++)
            list.add(f[i]);

        Collections.sort(list,new Comparator<Friend>() {

            public int compare(Friend arg0, Friend arg1) {

                return (int) (arg0.time - arg1.time);
            }
        });

        for(Friend l: list)
        {
            System.out.println("Name: "+l.name+", Time: "+l.time);
        }
    }
}