父類：

package com.java.day10;
// 使用者類：群主和成員類的父類
public class User {
    private String name;
    private int balance;

    public User() {
    }

    public User(String name, int balance) {
        this.name = name;
        this.balance = balance;
    }
    // 顯示餘額方法
    public void showBalance(){
        System.out.println(
 
"我叫："+name+","+"我有多少錢："+balance);
    }

    public String getName() {
        return name;
    }

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

    public int getBalance() {
        return balance;
    }

    public void setBalance(int balance) {
        this.balance = balance;
    }
}
 

群主類：

package com.java.day10;

import java.util.ArrayList;
// 群主類
public class GroupOwner extends User{
    public GroupOwner() {
    }

    public GroupOwner(String name, int balance) {
        super(name, balance);
    }
    // 發紅包
    public ArrayList<Integer> send(int totalMoney, int count){
        ArrayList
 
<Integer> arrayList = new ArrayList<>();
        // 先看自己的餘額是否大於所發金額
        int wallet = super.getBalance();  // 群主當前餘額
        if (totalMoney > wallet) {
            System.out.println("餘額不足");
            return arrayList;  // 返回空集合
        }
        // 扣錢,重新設定餘額
        super.setBalance(wallet-totalMoney);

        // 拆分紅包，每份多少錢
        // 平均數
        int avg = totalMoney / count;
        // 餘數，餘數放到最後一個紅包裡面
        int mod = totalMoney % count;
        for (int i = 0; i < count; i++) {
            // 如果是最後一個紅包，則把平均數和餘數加起來，放到最後一個數組裡面
            if (i == count-1) {
                arrayList.add(avg+mod);
            }
            else {
                arrayList.add(avg);
            }
        }
        return arrayList;
    }
}

群成員類：

package com.java.day10;

import java.util.ArrayList;
import java.util.Random;
// 成員類
public class Member extends User{
    public Member() {
    }

    public Member(String name, int balance) {
        super(name, balance);
    }

    // 收紅包
    public void receive(ArrayList<Integer> arrayList){
        Random random = new Random();
        // 判斷集合為空
        if (arrayList.size() != 0) {
            // 隨機抽取紅包
            int index = random.nextInt(arrayList.size());
            // 得到集合中的紅包
            int redPacket = arrayList.remove(index);
            // 當前成員本來的錢
            int money = super.getBalance();
            // 原有的錢加上抽紅包的錢
            super.setBalance(money+redPacket);
        }
        else {
            System.out.println("集合為空");
        }

    }
}

主方法呼叫：

package com.java.day10;

import java.util.ArrayList;
// 主方法
public class MainRadPacket {
    public static void main(String[] args) {
        GroupOwner groupOwner = new GroupOwner("土豪",100);
        Member memberOne = new Member("成員1",0);
        Member memberTwo = new Member("成員2",0);
        Member memberThree = new Member("成員3",0);
        // 發之前顯示餘額
        groupOwner.showBalance();
        memberOne.showBalance();
        memberTwo.showBalance();
        memberThree.showBalance();
        System.out.println("===================================================");
        // 群主發紅包總共20元，發3個
        ArrayList<Integer> list = groupOwner.send(20,3);
        // 接收紅包
        groupOwner.showBalance();
        memberOne.receive(list);
        memberTwo.receive(list);
        memberThree.receive(list);
        // 接收後，顯示餘額
        memberOne.showBalance();
        memberTwo.showBalance();
        memberThree.showBalance();
    }
}

執行結果：