Java多线程同步学习 取款例子

/**
 * 线程同步学习
 * @author Administrator
 *
 */
public class Crow_Thread {
    /**
     * 测试
     */
    public static void main(String[] args) {
        //例如张三的用户
        Account account = new Account();
        //张三的姐姐拥有张三的银行用户
        Thread t1 = new Thread(new Bank1(account));
        //张三的哥哥拥有张三的银行用户
        Thread t2 = new Thread(new Bank2(account));
        //张三的姐姐去取钱
        t1.start();
        //张三的哥哥去取钱
        t2.start();
    }
}


/**
 * 账户
 * @author Administrator
 *
 */
class Account{
    private float money =    1000f;

    public float getMoney() {
        return money;
    }



    public void setMoney(float money) {
        this.money = money;
    }


    /**
     * synchronized<---设置同步
     * @param price
     */
    public synchronized void putMoney(float price){
        if(money>=price){
            try {
                Thread.sleep(1000);
            } catch (Exception e) {
                // TODO: handle exception
            }
            System.out.println("被取走"+price+"元");
            money-=price;
        }else{
            System.out.println("当前余额不足,剩下:"+money+"元");
        }
    }
    
}
/**
 * 柜台1
 * @author Administrator
 *
 */
class Bank1 implements Runnable{
    private Account account;
    
    public Account getAccount() {
        return account;
    }

    public void setAccount(Account account) {
        this.account = account;
    }

    public Bank1(Account account) {
        super();
        this.account = account;
    }

    @Override
    public void run() {
        System.out.println("从银行1来取："+800+"块钱");
        //柜台2想去取走800块钱
        account.putMoney(800);
        System.out.println("剩余："+account.getMoney());
    }
    
}
/**
 * 柜台2
 * @author Administrator
 *
 */
class Bank2 implements Runnable{
    private Account account;
    
    public Account getAccount() {
        return account;
    }

    public void setAccount(Account account) {
        this.account = account;
    }

    public Bank2(Account account) {
        super();
        this.account = account;
    }

    @Override
    public void run() {
        System.out.println("从银行2来取："+700+"块钱");
        //柜台2想去取走700块钱
        account.putMoney(700);
        System.out.println("剩余："+account.getMoney());
    }
    
}

输出的是

从银行1来取：800块钱
从银行2来取：700块钱
被取走800.0元
剩余：200.0
当前余额不足,剩下:200.0元
剩余：200.0

 

如果不在取钱方法加 synchronized 关键字

输出的是

从银行1来取：800块钱
从银行2来取：700块钱
被取走800.0元
剩余：200.0
被取走700.0元
剩余：-500.0