哪位给看下这个示例程序
谁愿意帮我看下这个示例程序，
Bank类中的成员函数transfer里面
while (accounts[from] < amount)
wait();
用来阻塞钱数不够的操作
但是为何这里要用while呢？
谁能帮忙解释下
谢了


/**
* @version 1.20 1999-04-26
* @author Cay Horstmann
*/

public class SynchBankTest
{ public static void main(String[] args)
{ Bank b = new Bank(NACCOUNTS, INITIAL_BALANCE);
int i;
for (i = 0; i < NACCOUNTS; i++)
{ TransferThread t = new TransferThread(b, i,
INITIAL_BALANCE);
t.setPriority(Thread.NORM_PRIORITY + i % 2);
t.start();
}
}

public static final int NACCOUNTS = 10;
public static final int INITIAL_BALANCE = 10000;
}

class Bank
{ public Bank(int n, int initialBalance)
{ accounts = new int[n];
int i;
for (i = 0; i < accounts.length; i++)
accounts[i] = initialBalance;
ntransacts = 0;
}

public synchronized void transfer(int from, int to, int amount)
{ try
{ while (accounts[from] < amount)
wait();
accounts[from] -= amount;
accounts[to] += amount;
ntransacts++;
notifyAll();
if (ntransacts % NTEST == 0) test();
}
catch(InterruptedException e) {}
}

public synchronized void test()
{ int sum = 0;

for (int i = 0; i < accounts.length; i++)
sum += accounts[i];

System.out.println( "Transactions: " + ntransacts
+ " Sum: " + sum);
}

public int size()
{ return accounts.length;
}

public static final int NTEST = 10000;
private final int[] accounts;
private long ntransacts = 0;
}

class TransferThread extends Thread
{ public TransferThread(Bank b, int from, int max)
{ bank = b;
fromAccount = from;
maxAmount = max;
}

public void run()
{ try
{ while (!interrupted())
{ int toAccount = (int)(bank.size() * Math.random());
int amount = (int)(maxAmount * Math.random());
bank.transfer(fromAccount, toAccount, amount);
sleep(1);
}
}
catch(InterruptedException e) {}
}

private Bank bank;
private int fromAccount;
private int maxAmount;
}



[解决办法]
while (accounts[from] < amount)
wait();

这表示在notify的时候会判断while的条件是不是还是满足，如果还是满足，则继续wait，直到notify以后条件不再满足。
如果用if的话，一旦nitify以后，不管条件是否满足，都会执行后面的语句了。