《Java多线程编程核心技术》读后感（九）

 

 

当interrupt方法遇到wait方法

当线程呈wait()状态时，调用线程对象的interrupt（）会出现InterruptedException异常

package Third;

public class Service {

    public void testMethod(Object lock) {
        try {
            synchronized (lock) {
                System.out.println("begin wait()");
                lock.wait();
                System.out.println("  end wait()");
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
            System.out.println("出现异常了，因为呈wait状态的线程被interrupt了！");
        }
    }

}

package Third;

public class ThreadA extends Thread {

    private Object lock;

    public ThreadA(Object lock) {
        super();
        this.lock = lock;
    }

    @Override
    public void run() {
        Service service = new Service();
        service.testMethod(lock);
    }

}

package Third;

public class Test {

    public static void main(String[] args) {

        try {
            Object lock = new Object();

            ThreadA a = new ThreadA(lock);
            a.start();

            Thread.sleep(5000);

            a.interrupt();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }

}

只通知一个线程

调用方法notify()一次只随机通知一个线程进行唤醒

package Third;

public class Service {

    public void testMethod(Object lock) {
        try {
            synchronized (lock) {
                System.out.println("begin wait() ThreadName="
                        + Thread.currentThread().getName());
                lock.wait();
                System.out.println("  end wait() ThreadName="
                        + Thread.currentThread().getName());
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

}

package Third;

public class ThreadA extends Thread {
    private Object lock;

    public ThreadA(Object lock) {
        super();
        this.lock = lock;
    }

    @Override
    public void run() {
        Service service = new Service();
        service.testMethod(lock);
    }

}

package Third;

public class ThreadB extends Thread {
    private Object lock;

    public ThreadB(Object lock) {
        super();
        this.lock = lock;
    }

    @Override
    public void run() {
        Service service = new Service();
        service.testMethod(lock);
    }

}

package Third;

public class ThreadC extends Thread {
    private Object lock;

    public ThreadC(Object lock) {
        super();
        this.lock = lock;
    }

    @Override
    public void run() {
        Service service = new Service();
        service.testMethod(lock);
    }

}

package Third;

public class NotifyThread extends Thread {
    private Object lock;

    public NotifyThread(Object lock) {
        super();
        this.lock = lock;
    }

    @Override
    public void run() {
        synchronized (lock) {
            lock.notify();

        }
    }

}

package Third;

public class Test {

    public static void main(String[] args) throws InterruptedException {

        Object lock = new Object();

        ThreadA a = new ThreadA(lock);
        a.start();

        ThreadB b = new ThreadB(lock);
        b.start();

        ThreadC c = new ThreadC(lock);
        c.start();

        Thread.sleep(1000);

        NotifyThread notifyThread = new NotifyThread(lock);
        notifyThread.start();

    }

}

唤醒所有线程

package Third;

public class NotifyThread extends Thread {
    private Object lock;

    public NotifyThread(Object lock) {
        super();
        this.lock = lock;
    }

    @Override
    public void run() {
        synchronized (lock) {
            lock.notifyAll();

        }
    }

}

wait(long)的使用

功能是等待某一时间内是否有线程对锁进行唤醒，如果超过这个时间则自动唤醒

当然也可以由其他线程进行唤醒

package Third;

public class MyRunnable {
    static private Object lock = new Object();
    static private Runnable runnable1 = new Runnable() {
        @Override
        public void run() {
            try {
                synchronized (lock) {
                    System.out.println("wait begin timer="
                            + System.currentTimeMillis());
                    lock.wait(5000);
                    System.out.println("wait   end timer="
                            + System.currentTimeMillis());
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    };

    static private Runnable runnable2 = new Runnable() {
        @Override
        public void run() {
            synchronized (lock) {
                System.out.println("notify begin timer="
                        + System.currentTimeMillis());
                lock.notify();
                System.out.println("notify   end timer="
                        + System.currentTimeMillis());
            }
        }
    };

    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(runnable1);
        t1.start();
        Thread.sleep(3000);
        Thread t2 = new Thread(runnable2);
        t2.start();
    }

}

 通知过早

package Third;

public class MyRun {

    private String lock = new String("");
    

    private Runnable runnableA = new Runnable() {
        @Override
        public void run() {
            try {
                synchronized (lock) {
                
                        System.out.println("begin wait");
                        lock.wait();
                        System.out.println("end wait");
                    
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    };

    private Runnable runnableB = new Runnable() {
        @Override
        public void run() {
            synchronized (lock) {
                System.out.println("begin notify");
                lock.notify();
                System.out.println("end notify");
                

            }
        }
    };

    public static void main(String[] args) throws InterruptedException {

        MyRun run = new MyRun();

        Thread a = new Thread(run.runnableA);
        a.start();

        

        Thread b = new Thread(run.runnableB);
        b.start();

    }

}

package Third;

public class MyRun {

    private String lock = new String("");
    

    private Runnable runnableA = new Runnable() {
        @Override
        public void run() {
            try {
                synchronized (lock) {
                
                        System.out.println("begin wait");
                        lock.wait();
                        System.out.println("end wait");
                    
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    };

    private Runnable runnableB = new Runnable() {
        @Override
        public void run() {
            synchronized (lock) {
                System.out.println("begin notify");
                lock.notify();
                System.out.println("end notify");
                

            }
        }
    };

    public static void main(String[] args) throws InterruptedException {

        MyRun run = new MyRun();

        Thread a = new Thread(run.runnableA);
        a.start();

        Thread.sleep(100);

        Thread b = new Thread(run.runnableB);
        b.start();

    }

}

如果先通知了，则wait方法也就没有必要执行了

package Third;

public class MyRun {

    private String lock = new String("");
    private boolean isFirstRunB = false;

    private Runnable runnableA = new Runnable() {
        @Override
        public void run() {
            try {
                synchronized (lock) {
                    while (isFirstRunB == false) {
                        System.out.println("begin wait");
                        lock.wait();
                        System.out.println("end wait");
                    }
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    };

    private Runnable runnableB = new Runnable() {
        @Override
        public void run() {
            synchronized (lock) {
                System.out.println("begin notify");
                lock.notify();
                System.out.println("end notify");
                isFirstRunB = true;

            }
        }
    };

    public static void main(String[] args) throws InterruptedException {

        MyRun run = new MyRun();
        Thread b = new Thread(run.runnableB);
        b.start();
        Thread.sleep(100);
        Thread a = new Thread(run.runnableA);
        a.start();

    }

}

等待wait条件发生变化

 在使用wait/notify模式时，还需要注意另外一种情况。也就是wait等待的条件发生了变化，也容易造成程序逻辑混乱

package Third;

public class Add {
    
    private String lock;

    public Add(String lock) {
        super();
        this.lock = lock;
    }

    public void add() {
        synchronized (lock) {
            ValueObject.list.add("anyString");
            lock.notifyAll();
        }
    }
    
}

package Third;

public class Subtract {
    
    private String lock;

    public Subtract(String lock) {
        super();
        this.lock = lock;
    }

    public void subtract() {
        try {
            synchronized (lock) {
                if (ValueObject.list.size() == 0) {
                    System.out.println("wait begin ThreadName="
                            + Thread.currentThread().getName());
                    lock.wait();
                    System.out.println("wait   end ThreadName="
                            + Thread.currentThread().getName());
                }
                ValueObject.list.remove(0);
                System.out.println("list size=" + ValueObject.list.size());
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }


}

package Third;

import java.util.ArrayList;
import java.util.List;

public class ValueObject {
    
    public static List list = new ArrayList();

}

package Third;

public class ThreadAdd extends Thread {

    private Add p;

    public ThreadAdd(Add p) {
        super();
        this.p = p;
    }

    @Override
    public void run() {
        p.add();
    }

}

package Third;

public class ThreadSubtract extends Thread {

    private Subtract r;

    public ThreadSubtract(Subtract r) {
        super();
        this.r = r;
    }

    @Override
    public void run() {
        r.subtract();
    }

}

package Third;

public class Run {

    public static void main(String[] args) throws InterruptedException {

        String lock = new String("");

        Add add = new Add(lock);
        Subtract subtract = new Subtract(lock);

        ThreadSubtract subtract1Thread = new ThreadSubtract(subtract);
        subtract1Thread.setName("subtract1Thread");
        subtract1Thread.start();

        ThreadSubtract subtract2Thread = new ThreadSubtract(subtract);
        subtract2Thread.setName("subtract2Thread");
        subtract2Thread.start();

        Thread.sleep(1000);

        ThreadAdd addThread = new ThreadAdd(add);
        addThread.setName("addThread");
        addThread.start();

    }

}

 

package Third;

public class Subtract {
    
    private String lock;

    public Subtract(String lock) {
        super();
        this.lock = lock;
    }

    public void subtract() {
        try {
            synchronized (lock) {
                while (ValueObject.list.size() == 0) {
                    System.out.println("wait begin ThreadName="
                            + Thread.currentThread().getName());
                    lock.wait();
                    System.out.println("wait   end ThreadName="
                            + Thread.currentThread().getName());
                }
                ValueObject.list.remove(0);
                System.out.println("list size=" + ValueObject.list.size());
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }


}

生产者/消费者模式实现

1、一生产与一消费：操作值

package Third;

//生产者
public class P {

    private String lock;

    public P(String lock) {
        super();
        this.lock = lock;
    }

    public void setValue() {
        try {
            synchronized (lock) {
                if (!ValueObject.value.equals("")) {
                    lock.wait();
                }
                String value = System.currentTimeMillis() + "_"
                        + System.nanoTime();
                System.out.println("set的值是" + value);
                ValueObject.value = value;
                lock.notify();
            }

        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

}

package Third;

//消费者
public class C {

    private String lock;

    public C(String lock) {
        super();
        this.lock = lock;
    }

    public void getValue() {
        try {
            synchronized (lock) {
                if (ValueObject.value.equals("")) {
                    lock.wait();
                }
                System.out.println("get的值是" + ValueObject.value);
                ValueObject.value = "";
                lock.notify();
            }

        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

}

package Third;

public class ValueObject {

    public static String value = "";

}

package Third;

public class ThreadP extends Thread {

    private P p;

    public ThreadP(P p) {
        super();
        this.p = p;
    }

    @Override
    public void run() {
        while (true) {
            p.setValue();
        }
    }

}

package Third;

public class ThreadC extends Thread {

    private C r;

    public ThreadC(C r) {
        super();
        this.r = r;
    }

    @Override
    public void run() {
        while (true) {
            r.getValue();
        }
    }

}

package Third;

public class Run {

    public static void main(String[] args) {

        String lock = new String("");
        P p = new P(lock);
        C r = new C(lock);

        ThreadP pThread = new ThreadP(p);
        ThreadC rThread = new ThreadC(r);

        pThread.start();
        rThread.start();
    }

}

在控制台中打印的日志get和set是交替运行的

2、多生产与多消费：操作值-假死

“”假死“”的现象其实就是线程进入waiting等待状态，如果全部线程都进入waiting状态，则程序就不再执行任何业务功能了，整个项目呈停止状态

package Third;

//消费者
public class C {

    private String lock;

    public C(String lock) {
        super();
        this.lock = lock;
    }

    public void getValue() {
        try {
            synchronized (lock) {
                while (ValueObject.value.equals("")) {
                    System.out.println("消费者 "
                            + Thread.currentThread().getName() + " WAITING了☆");
                    lock.wait();
                }
                System.out.println("消费者 " + Thread.currentThread().getName()
                        + " RUNNABLE了");
                ValueObject.value = "";
                lock.notify();
            }

        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

}

package Third;

//生产者
public class P {

    private String lock;

    public P(String lock) {
        super();
        this.lock = lock;
    }

    public void setValue() {
        try {
            synchronized (lock) {
                while (!ValueObject.value.equals("")) {
                    System.out.println("生产者 "
                            + Thread.currentThread().getName() + " WAITING了★");
                    lock.wait();
                }
                System.out.println("生产者 " + Thread.currentThread().getName()
                        + " RUNNABLE了");
                String value = System.currentTimeMillis() + "_"
                        + System.nanoTime();
                ValueObject.value = value;
                lock.notify();
            }

        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

}

package Third;

public class ValueObject {

    public static String value = "";

}

package Third;

public class ThreadP extends Thread {

    private P p;

    public ThreadP(P p) {
        super();
        this.p = p;
    }

    @Override
    public void run() {
        while (true) {
            p.setValue();
        }
    }

}

package Third;

public class ThreadC extends Thread {

    private C r;

    public ThreadC(C r) {
        super();
        this.r = r;
    }

    @Override
    public void run() {
        while (true) {
            r.getValue();
        }
    }

}

package Third;

public class Run {

    public static void main(String[] args) throws InterruptedException {

        String lock = new String("");
        P p = new P(lock);
        C r = new C(lock);

        ThreadP[] pThread = new ThreadP[2];
        ThreadC[] rThread = new ThreadC[2];

        for (int i = 0; i < 2; i++) {
            pThread[i] = new ThreadP(p);
            pThread[i].setName("生产者" + (i + 1));

            rThread[i] = new ThreadC(r);
            rThread[i].setName("消费者" + (i + 1));

            pThread[i].start();
            rThread[i].start();
        }

        Thread.sleep(5000);
        Thread[] threadArray = new Thread[Thread.currentThread()
                .getThreadGroup().activeCount()];
        Thread.currentThread().getThreadGroup().enumerate(threadArray);

        for (int i = 0; i < threadArray.length; i++) {
            System.out.println(threadArray[i].getName() + " "
                    + threadArray[i].getState());
        }
    }

}

 

假死出现的主要原因是有可能连续唤醒同类

多生产与多消费：操作值

将上面项目的P.java和C.java文件中的notify()改成notifyAll()即可，不光通知同类线程，也包括异类