同步线程的synchronized关键字的使用

public class FetchMoney
{
public static void main(String args[])
{
BankCard card=new BankCard();
MoneyThread thread1=new MoneyThread(card);//柜台
MoneyThread thread2=new MoneyThread(card);//ATM机
thread1.start();
thread2.start();
}
}
class BankCard
{
private int money=1000;
public  synchronized int getMoney(int number)//对访问该方法的对象进行上锁，直至线程访问方法完毕，才会解锁，让其他线程进入访问
{
if(number<0)
return -1;
else if(number>money)
return -2;
else
{
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
money =money-number;
return number;
}
}
}
class MoneyThread extends Thread
{
private BankCard bankcard;
public MoneyThread(BankCard bankcard)
{
this.bankcard=bankcard;
}
@Override
public void run() {
// TODO Auto-generated method stub
System.out.println(bankcard.getMoney(800));
}
}