多线程之间的交互

系统管理员 2023-08-17 17:07 22阅读 0赞

像在一个参数版本中，中断和虚假唤醒是可能的，并且该方法应该始终在循环中使用：

synchronized (obj) {
             while (<condition does not hold>)
                 obj.wait();
             ... // Perform action appropriate to condition
         }

不能使用if来判断，应该使用while。

在多线程中判断使用while

package cn.zh.juc1205;
    
    
    class Aircondition {
    
        private int number = 0;
    
        public synchronized void increment() throws Exception {
            //判断
            while (number != 0) {
                this.wait();
            }
            number++;
            System.out.println(Thread.currentThread().getName()+"\t" +number);
            //通知
            this.notifyAll();
        }
        public  synchronized void decrement() throws Exception {
            //判断
            while (number == 0) {
                this.wait();
            }
            number--;
            System.out.println(Thread.currentThread().getName()+"\t" +number);
            //通知
            this.notifyAll();
        }
    }
    /**
     *题目：现在两个线程，可以操作初始值为零的一个变量，
     * 实现一个线程对该变量加1，一个线程对该变量减1，
     * 实现交替，来10轮，变量初始值为零
     * 1.高内聚低耦合前提下，线程操作资源类
     * 2.判断/干活/通知
     * 3.防止虚假唤醒
     */
    public class ProdConsumerDemo04 {
    
        public static void main(String[] args) throws Exception {
    
            Aircondition aircondition = new Aircondition();
    
            new Thread(()->{
                for (int i = 1; i <= 10; i++) {
                    try {
                        aircondition.increment();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            },"A").start();
            new Thread(()->{
                for (int i = 1; i <= 10; i++) {
                    try {
                        aircondition.decrement();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            },"B").start();
            new Thread(()->{
                for (int i = 1; i <= 10; i++) {
                    try {
                        aircondition.increment();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            },"C").start();
            new Thread(()->{
                for (int i = 1; i <= 10; i++) {
                    try {
                        aircondition.decrement();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            },"D").start();
    
    
        }
    }

package cn.zh.juc1205;
    
    
    import java.util.concurrent.locks.Condition;
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    
    class ShareData {
    
        private int number = 1;//A:1 B:2 C:3定义标志位
        private Lock lock = new ReentrantLock();
        private Condition c1 = lock.newCondition();
        private Condition c2 = lock.newCondition();
        private Condition c3 = lock.newCondition();
    
    
        public void print5() {
            lock.lock();
            try {
                //1.判断
                while (number != 1) {
                    c1.await();
                }
                //2.打印五次
                for (int i = 0; i < 5; i++) {
                    System.out.println(Thread.currentThread().getName()+"\t"+i);
                }
                //3.通知 如何通知第二个
                number = 2;
    
                c2.signalAll();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }
        }
        public void print10() {
            lock.lock();
            try {
                //1.判断
                while (number != 2) {
                    c2.await();
                }
                //2.打印五次
                for (int i = 0; i < 10; i++) {
                    System.out.println(Thread.currentThread().getName()+"\t"+i);
                }
                //3.通知 如何通知第二个
                number = 3;
    
                c3.signalAll();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }
        }
        public void print15() {
            lock.lock();
            try {
                //1.判断
                while (number != 3) {
                    c3.await();
                }
                //2.打印五次
                for (int i = 0; i < 15; i++) {
                    System.out.println(Thread.currentThread().getName()+"\t"+i);
                }
                //3.通知 如何通知第二个
                number = 1;
    
                c1.signalAll();
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }
        }
    
    
    }
    
    /**
     * 备注多线程之间按顺序调用 实现A->B->C
     * 三个线程启动，要求如下：
     * AA打印5次，BB打印10次，CC打印15次
     * 接着
     *  AA打印5次，BB打印10次，CC打印15次
     *
     */
    public class ConditionDemo {
    
        public static void main(String[] args) {
            ShareData shareData = new ShareData();
    
            new Thread(()->{
                for (int i = 1;i <= 10; i++) {
                    shareData.print5();
                }
    
            },"A").start();
            new Thread(()->{
                for (int i = 1;i <= 10; i++) {
                    shareData.print10();
                }
    
            },"B").start();
            new Thread(()->{
                for (int i = 1;i <= 10; i++) {
                    shareData.print15();
                }
    
            },"C").start();
        }
    }