java 线程通信 - 取钱，存钱问题

问题：每次先存一次钱，然后再取一次钱。两个线程交替进行。

方式一：使用同步监视器对象的等待 wait方法和唤醒 notifyAll方式来实现。

1. 定义falg 标签来标记应该取钱还是存钱。开始为false ，表示先存钱

2.每次操作时，进行判断，取钱应该满足 falg = true ，存钱应该满足 falg = false；要用while 进行判断！！不要用if - else 。

我在其他书上看到了 if - else 的形式，这样条件为 false --> wait -> notify ->方法结束。

使用while时，条件为false -> wait -> notify -> 重新判断条件 -- 这样线程数量不会减少。

package synchronizedxx;

public class Account {
	private String accountNo;
	private double balance;
	private boolean falg = false;
	
	public Account(String accountNo,double balance){
		this.accountNo = accountNo;
		this.balance = balance;
	}
	
	public synchronized void draw(double drawAmont){
		
		try {
			while (!falg)
				wait();
			{
				System.out.println(Thread.currentThread().getName()+ " 取钱:"+drawAmont);
				falg = !falg;
				balance -= drawAmont;
				System.out.println("余额为："+balance);
				notifyAll();
			}
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
	
	public synchronized void deposit(double drawAmont){
		
		try {
			while (falg)
				wait();
			{
				System.out.println(Thread.currentThread().getName()+ " 存钱:"+drawAmont);
				falg = !falg;
				balance -= drawAmont;
				System.out.println("余额为："+balance);
				notifyAll();
			}
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}

}

package synchronizedxx;

public class DrawThread extends Thread{
	
	private Account account; 
	private double drawAmont;
	
	public DrawThread(String name,Account account,double drawAmont) {
		super(name);
		this.account = account;
		this.drawAmont = drawAmont ;
	}
	
	@Override
	public void run() {
		for (int i=0;i<10;i++){
			
			System.out.println("draw:"+i);
			account.draw(drawAmont);
		}
	}
}

package synchronizedxx;

public class DepositThread extends Thread{
	
	private Account account; 
	private double depositAmont;
	
	public DepositThread(String name,Account account,double depositAmont) {
		super(name);
		this.account = account;
		this.depositAmont = depositAmont ;
	}
	
	@Override
	public void run() {
		for (int i=0;i<10;i++){
			System.out.println("deposit:"+i);
			account.deposit(depositAmont);
			
		}
	}
}

package synchronizedxx;

public class DrawTest {
	
	public static void main(String[] args) {
		Account account = new Account("123456",0);
		
		new DrawThread("取钱者", account, 800).start();
		new DepositThread("存钱者",account,800).start();
	}
}

java 线程通信 - 取钱，存钱问题

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