用JAVA中的多线程示例银行取款问题

/** 
*@authorleno 
*账户类 
*默认有余额，可以取款 
*/ 
class Account { 
    private float balance = 1000; 

    public float getBalance() { 
      return balance; 
    } 

    public void setBalance(float balance) { 
      this.balance = balance; 
    } 
    
    /** 
    *取款的方法需要同步 
    *@parammoney 
    */ 
    public synchronized void withdrawals(float money) 
    { 
      if(balance>=money) 
      { 
          System.out.println("被取走"+money+"元!"); 
          try { 
              Thread.sleep(1000); 
          } catch (InterruptedException e) { 
              // TODO Auto-generated catch block 
              e.printStackTrace(); 
          } 
          balance-=money; 
      } 
      else  { 
          System.out.println("对不起,余额不足!"); 
      } 
    } 
    
} 

/** 
*@authorleno 
*银行卡 
*/ 
class TestAccount1 extends Thread { 

    private Account account; 
    
    
    public TestAccount1(Account account) { 
      this.account = account; 
    } 


    @Override 
    public void run() { 
      account.withdrawals(800); 
      System.out.println("余额为:"+account.getBalance()+"元!"); 
    }  
} 
/** 
*@authorleno 
*存折 
*/ 
class TestAccount2 extends Thread { 

    private Account account; 
    public TestAccount2(Account account) { 
          this.account = account; 
      } 
    @Override 
    public void run() { 
      account.withdrawals(700); 
      System.out.println("余额为:"+account.getBalance()+"元!"); 
    }  
} 

public class Test { 
    public static void main(String[] args) { 
      Account account = new Account(); 
      TestAccount1 testAccount1 = new TestAccount1(account); 
      testAccount1.start(); 
      TestAccount2 testAccount2 = new TestAccount2(account); 
      testAccount2.start(); 
    } 
}