三大不安全案例

一、买票

package com.massimo.threadsyn;

//不安全的买票
public class UnsafeBuyTicket{

    public static void main(String[] args) {
        BuyTicket station = new BuyTicket();

        new Thread(station,"Massimo").start();
        new Thread(station,"Tom").start();
        new Thread(station,"Jack").start();

    }
}

class BuyTicket implements Runnable{

    //票
    private int ticketNums = 10;
    boolean flag = true;//外部停止方式

    //买票
    @Override
    public void run() {
        while (flag){
            try {
                buy();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    private void buy() throws InterruptedException {
        //判断是否有票
        if (ticketNums <= 0){
            flag = false;
            return;
        }
        //模拟延时
        Thread.sleep(100);
        System.out.println(Thread.currentThread().getName() + "拿到了第" + ticketNums-- + "张票");
    }
}

效果：

二、取钱

package com.massimo.threadsyn;

//模拟不安全取钱
public class UnsafeBank {
    public static void main(String[] args) {
        //账户
        Account account = new Account(100, "结婚基金");

        Drawing you = new Drawing(account ,50, "You");
        Drawing girlfriend = new Drawing(account ,100, "girlfriend");

        you.start();
        girlfriend.start();
    }
}

//账户
class Account{
    int money;//余额
    String name;//卡名

    public Account(int money, String name) {
        this.money = money;
        this.name = name;
    }
}

//银行：模拟取款
class Drawing extends Thread{

    Account account;//账户
    int drawingMoney;//取了多少钱
    int nowMoney;//现在手里有多少钱

    public Drawing(Account account , int drawingMoney , String name){
        super(name);
        this.account = account;
        this.drawingMoney = drawingMoney;
    }

    @Override
    public void run() {
        //判断有没有钱
        if (account.money - drawingMoney < 0){
            System.out.println(Thread.currentThread().getName() + "钱不够，取不了");
            return;
        }

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        //卡内余额  =  余额  - 你取的钱
        account.money = account.money - drawingMoney;
        //你手里的钱
        nowMoney = nowMoney + drawingMoney;

        System.out.println(account.name + "余额为：" + account.money);
        System.out.println(this.getName() + "手里的钱：" + nowMoney);
    }
}

效果：

三、不安全的集合

package com.massimo.threadsyn;

import java.util.ArrayList;
import java.util.List;

public class UnsafeList {
    public static void main(String[] args) {
        List<String> list = new ArrayList<String>();
        for (int i = 0; i < 10000; i++) {
            new Thread(()->{
                list.add(Thread.currentThread().getName());
            }).start();
        }
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(list.size());
    }
}

效果：