本文详细介绍Java多线程同步中的两个特殊类
public class ATM
{
Account acc;
//作为演示，省略了密码验证
public boolean login(String name)
{
if (acc != null) throw new IllegalArgumentException("Already logged in!");
acc = new Account(name);
return true;
}
public void deposit(float amt)
{
acc.deposit(amt);
}
public void withdraw(float amt) throws InsufficientBalanceException
{
acc.withdraw(amt);
}
public float getBalance()
{
return acc.getBalance();
}
public void logout ()
{
acc = null;
}
}下面是ATMTester，在ATMTester中首先生成了10个ATM实例，然后启动10个线程，同时登录John的账户，先查询余额，然后，再提取余额的80％，然后再存入等额的款（以维持最终的余额的不变）。按照我们的预想，应该不会发生金额不足的问题。首先看代码：
public class ATMTester
{
private static final int NUM_OF_ATM = 10;
public static void main(String[] args)
{
ATMTester tester = new ATMTester();
final Thread thread[] = new Thread[NUM_OF_ATM];
final ATM atm[] = new ATM[NUM_OF_ATM];
for (int i=0; i<NUM_OF_ATM; i++)
{
atm[i] = new ATM();
thread[i] = new Thread(tester.new Runner(atm[i]));
thread[i].start();
}
}
class Runner implements Runnable
{
ATM atm;
Runner(ATM atm)
{
this.atm = atm;
}
public void run()
{
atm.login("John");
//查询余额
float bal = atm.getBalance();
try
{
Thread.sleep(1);
//模拟人从查询到取款之间的间隔
}
catch (InterruptedException e)
{ // ignore it }
try
{
System.out.println("Your balance is:" + bal);
System.out.println("withdraw:" + bal * 0.8f);
atm.withdraw(bal * 0.8f);
System.out.println("deposit:" + bal * 0.8f);
atm.deposit(bal * 0.8f);
}
catch (InsufficientBalanceException e1)
{
System.out.println("余额不足！");
}
finally
{ atm.logout(); }
}
}
}运行ATMTester，结果如下（每次运行结果都有所差异）：
责编：豆豆技术应用
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