Java 练习(线程的同步)

银行有一个账户。
有两个储户分别向同一个账户存3000元，每次存1000，存3次。每次存完打印账户余额。
问题:该程序是否有安全问题,如果有，如何解决?

分析:

1. 是否是多线程问题?是，两个储户线程
2. 是否有共享数据?有，账户(或账户余额)
3. 是否有线程安全问题?有
4. 需要考虑如何解决线程安全问题?同步机制:有三种方式。

使用继承 Thread 方式

package com.klvchen.exer;

class Account{
    private double balance;

    public Account(double balance){
        this.balance = balance;
    }

    //存钱
    public synchronized void deposit(double amt) {
        if(amt > 0){
            balance += amt;

            try{
                Thread.sleep(100);
            }catch (InterruptedException e){
                e.printStackTrace();
            }


            System.out.println(Thread.currentThread().getName() + " 存钱成功，余额为: " + balance);
        }
    }

}

class Customer extends Thread{

    private Account acct;

    public Customer(Account acct){
        this.acct = acct;
    }

    @Override
    public void run(){
        for (int i = 0; i < 3; i++){
            acct.deposit(1000);

        }
    }
}


public class AccountTest {
    public static void main(String[] args) {
        Account acct = new Account(0);
        Customer c1 = new Customer(acct);
        Customer c2 = new Customer(acct);

        c1.setName("甲");
        c2.setName("乙");

        c1.start();
        c2.start();
    }
}

实现Runnable接口的方式

package com.klvchen.exer;

class Account{
    private double balance;

    public Account(double balance){
        this.balance = balance;
    }

    //存钱
    public synchronized void deposit(double amt) {
        if(amt > 0){
            balance += amt;

            try{
                Thread.sleep(1000);
            }catch (InterruptedException e){
                e.printStackTrace();
            }


            System.out.println(Thread.currentThread().getName() + " 存钱成功，余额为: " + balance);
        }
    }

}

class Customer implements Runnable{

    private Account acct;

    public Customer(Account acct){
        this.acct = acct;
    }

    @Override
    public void run(){
        for (int i = 0; i < 3; i++){
            acct.deposit(1000);

        }
    }
}


public class AccountTest {
    public static void main(String[] args) {
        Account acct = new Account(0);
        Customer c = new Customer(acct);

        Thread t1 = new Thread(c);
        Thread t2 = new Thread(c);

        t1.setName("甲");
        t2.setName("乙");

        t1.start();
        t2.start();
    }
}