同步方法及同步块

同步方法锁的是this当前对象,类本身

同步块可以锁任何对象

锁的对象就是变化的量，需要增删改查的对象

package com.syn;

//不安全买票
public class UnSafeBuyTicket {
    public static void main(String[] args) {
        BuyTicket buyTicket = new BuyTicket();

        new Thread(buyTicket,"苦逼的我").start();
        new Thread(buyTicket,"牛逼的你们").start();
        new Thread(buyTicket,"可恶的黄牛党").start();
    }
}


class BuyTicket implements Runnable{
    //票
    private int num = 10;
    boolean flag = true;    //外部停止方式

    @Override
    public void run() {
        while (flag) {
            buy();
        }
    }



    //synchronized,锁的是this
    private synchronized void buy(){
        while (flag) {
           //判断是否有票
            if(num<=0){
                flag=false;
                return;
            }

            //模拟延时
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            //买票
            System.out.println(Thread.currentThread().getName() + "" + num--);
        }
    }
}

package com.syn;


//不安全的取钱
//两个人去银行取钱，账号
public class UnSafeBank {
    public static void main(String[] args) {
        //账户
        Account account = new Account(1000,"结婚基金");

        Drawing you = new Drawing(account,50,"你");
        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;

    }

    //取钱
    //synchronized 默认锁的是this,类本身（Drawing银行）
    @Override
    public void run() {

        // **锁的对象就是变化的量，需要增删改查的对象**
        synchronized (account) {
            //判断账户里有没有钱
            if (account.money - drawingMoney < 0) {
                System.out.println(Thread.currentThread().getName() + "钱不够，取不了");
                return;
            }

            //sleep放大事情的发生性
            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 = 手里的钱 + 你取的钱
            nowMoney = nowMoney + drawingMoney;

            System.out.println(account.name + "余额为" + account.money);

            //Thread.currentThread().getName() = this.getName()
            System.out.println(this.getName() + "手里的钱" + nowMoney);

        }
    }
}

package com.syn;


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

//线程不安全的集合
public class UnSafeList {
    public static void main(String[] args) {
        List<String> list = new ArrayList<>();
        for (int i = 0; i < 10000; i++) {
            new Thread(()->{
                synchronized (list) {
                    list.add(Thread.currentThread().getName());
                }
            }).start();
        }

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(list.size());
    }
}