Comment implémenter une applet de retrait avec le multi-threading Java

public class Account {
    //封装账户编号，账户余额和两个成员变量
    private String accountNo;
    private double balance;

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

    public void setAccountNo(String accountNo)
    {
        this.accountNo=accountNo;
    }
    public void setBalance(double balance){
        this.balance=balance;
    }

    public String getAccountNo(){
        return accountNo;
    }
    public double getBalance(){
        return balance;
    }

    public int hashCode(){
        return accountNo.hashCode();
    }

    public boolean equals(Object obj){
        if(this==obj){
            return true;
        }
        if (obj!=null&&obj.getClass()==Account.class){
            Account target=(Account)obj;
            return target.getAccountNo().equals(accountNo);
        }
        return false;
    }

}

public class DrawThread extends Thread {
    //模拟用户账户
    private Account account;
    //当前取钱线程所希望的取钱数
    private double drawAmount;

    public DrawThread(String name, Account account, double drawAmount) {
        super(name);
        this.account = account;
        this.drawAmount = drawAmount;
    }

    //当多个线程修改同一个共享数据时，将涉及数据安全问题
    public void run() {
        //使用account作为同步监视器，任何线程进入下面同步代码块之前
        //必须先获得对account账户的锁定——其他线程无法获得锁，也就无法修改它
        synchronized (account) {
            if (account.getBalance() >= drawAmount) {
                //吐出钞票
                System.out.println(getName() + "取钱成功！吐出钞票：" + drawAmount);
        /*
        try {
           Thread.sleep(1);
           }catch (InterruptedException ex)
        {
            ex.printStackTrace();
        }
        */
                //修改余额
                account.setBalance(account.getBalance() - drawAmount);
                System.out.println("\t余额为：" + account.getBalance());
            } else {
                System.out.println(getName() + "取钱失败！余额不足！");
            }
        }
    }
}

public class DrawTest {
    public static void main(String[] args){
        //创建一个账户
        Account acct=new Account("1234567",1000);
        //模拟两个线程对同一个账户取钱
        new DrawThread("jack",acct,800).start();
        new DrawThread("rose",acct,800).start();
    }
}

synchronized (obj){
//需要执行的代码
}

Account acct=new Account("1234567",1000);
new DrawThread("jack",acct,800).start();
new DrawThread("rose",acct,800).start();