Java多线程练习1：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？

继承Thread类：需要new两个customer来对同一个账户Account进行存钱操作。

class Account{

    private double balance;

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

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

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

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

    }
}

class Customer extends Thread{

    private Account acc;

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

    private static ReentrantLock lock = new ReentrantLock();
    @Override
    public void run() {

        lock.lock();
        for(int i = 0; i < 3; i++){

            acc.deposit(1000);

        }
        lock.unlock();
    }
}

public class AccountTest {

    public static void main(String[] args) {
        Account allacc = new Account(0);

        Customer c1 = new Customer(allacc);
        Customer c2 = new Customer(allacc);

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

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

    }
}

实现Runnable接口：在创建实现类的对象customers后，需要将此对象作为参数传递到Thread类的构造器中，才能调用start()。

class BankAccount{
    private double balance;

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

    //存钱
    public void deposit(double money){
        if(money > 0){
            balance += money;
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "存钱，余额为：" + balance);
        }
    }
}

class Customers implements Runnable{

    private static ReentrantLock lock = new ReentrantLock();
    private BankAccount acc;

    public Customers(BankAccount acc) {
        this.acc = acc;
    }

    @Override
    public void run() {

        lock.lock();
        for (int i =0; i< 3;i++){
            acc.deposit(1000);
        }
        lock.unlock();

    }
}

public class AccountTest1 {

    public static void main(String[] args) {
        BankAccount acc = new BankAccount(0);
        Customers c1 = new Customers(acc);

        Thread t1 = new Thread(c1);
        Thread t2 = new Thread(c1);

        t1.setName("蛇");
        t2.setName("荷包蛋");

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

}