java - 将 Await、Signal、SignalAll 替换为 wait、notify 和 notifyAll

Question

我想用 wait(),notifyAll() (java 的默认监视器)替换 wait(),signalAll() 和下面列出的我的代码，问题是一旦线程进入等待状态。它永远不会再被通知..感谢您的帮助。

import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class AccountThreadCommunicationDefault {
    private static Account account = new Account();
    private static Random random = new Random();
    public static void main(String... args) {
        ExecutorService es = Executors.newFixedThreadPool(2);
        es.execute(new WithdrawTask());
        es.execute(new DepositTask());
        es.shutdown();
    }

    private static class WithdrawTask implements Runnable {
        public void run() {
            while (true) {
                account.withdraw(random.nextInt(600));
                try {
                    Thread.sleep(5000);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

        }
    }

    private static class DepositTask implements Runnable {
        public void run() {
            while (true) {
                account.deposit(random.nextInt(500));
                try {
                    Thread.sleep(5000);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    }

    private static class Account {
        private Integer balance = 500;
        private static Lock lock = new ReentrantLock();
        Condition condition = lock.newCondition();
        // private Object object = new Object();

        // public synchronized void deposit(int count) {
        public void deposit(int count) {
            try {
                lock.lock();
                System.out.print("当前账户余额：" + balance);
                balance += count;
                System.out.println(" 存款：" + count + " 账户余额(deposit)： "
                        + getBalance());
                // synchronized (object) {
                // object.notifyAll();
                // }
                synchronized (this) {
                    this.notify();
                }
            } catch (IllegalMonitorStateException e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }

        public void withdraw(int count) {
            try {
                lock.lock();
                while (balance < count) {

                    System.out.println("余额不足：" + getBalance() + " 等待存款..");
                    // synchronized (object) {
                    // object.wait();
                    // }
                    synchronized (this) {
                        this.wait();
                    }

                    System.out.print("当前账户余额：" + balance);
                    balance -= count;
                    System.out.println(" 取现：" + count + " 账户余额(withdraw)： "
                            + getBalance());
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }

        }

        public int getBalance() {
            return this.balance;
        }
    }

}

Answer 1

你陷入了僵局。 Withdraw 任务正在等待 Account 对象的监视器，同时保持 ReentrantLock 锁定。 Deposit 任务无法notify() Account 对象监视器，因为它无法锁定ReentrantLock。

您需要 wait() 和 notification() 用作互斥体的同一个对象。无论是 ReentrantLock 还是 Account 对象的监视器都没有关系。但它不会像你用两个不同的锁编写的那样工作。