java并发编程（更新）

概念理解：①串行程序②并发程序；

线程安全问题：

同一进程中的所有线程共享进程中的内存地址空间。如果没有明确的同步机制来管理共享数据，那么当一个线程正在使用某个变量时，另一个线程可能同时访问这个变量，造成不可预测的结果。

同步（Synchronous）:

异步（Asynchronous）:

并发（Concurrency）:

并行（Parallelism）:

临界区：临界区表示一种公共资源或公共数据，可以被多个线程交替使用。

阻塞（Blocking）：一个线程占用了临界区资源，其他所有需要这个资源的线程必须在这个临界区中等待；

非阻塞（Non-Blocking）：

java的内存模型JMM：

①原子性：一个线程进行操作，不该被其他线程干扰。

②可见性：当一个线程修改了某一个共享变量的值，其他线程能否立即知道这个共享变量已被修改。

③有序性：

进程：进程是线程的容器。程序是指令、数据及其组织形式的描述，进程是程序的实体。

线程状态：

线程操作API：

创建线程的方式：

new Thread(){//匿名内部类的方式，重载了run方法，run方法结束自动回收线程。

public void run(){

　　System.out.println("线程1");　　

}}.start();

new Thread(new Runnable(){//构造方法：Thread(Runnable target)
public void run() {
　　System.out.println("线程2");
}
}).start();

线程的终止：

Thread.stop()已废弃，stop强行终止线程，并且会立即释放这个线程所持有的锁（如果这些锁恰恰是用来维持对象的一致性的，其他线程就会读到不一致的对象）：

线程的终止应该由程序员自己决定。

（volatile关键字解释：）

线程中断：

interrupt()中断线程

isInterrupted()判断是否被中断

interrupted()判断是否被中断，并清除当前中断状态

等待（wait）和通知（notify、notifyAll）：

public class waitTest {
    final static Object obj=new Object();
    public static void main(String[] args) {
        new Thread(){
            public void run(){
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e1) {
                    e1.printStackTrace();
                }
                synchronized(obj){
                    System.out.println(System.currentTimeMillis()+" T2:start! notify one thread");
                    obj.notify();
                    System.out.println(System.currentTimeMillis()+" T2:end!");
                    try {
                        Thread.sleep(2000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }.start();
        new Thread(){
            public void run(){
                synchronized(obj){
                    System.out.println(System.currentTimeMillis()+" T1:start!");
                    try {
                        System.out.println(System.currentTimeMillis()+" T1 wait for obj!");
                        obj.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(System.currentTimeMillis()+" T1:end!");
                }
            }
        }.start();
    }
}

wait、notify、notifyAll是Object类的方法（由锁对象object调用），sleep、yeild是Thread类的方法；

obj.wait()和Thread.sleep()都能让线程等待若干时间。wait()可以被唤醒，并且释放目标对象的锁，而Thread.sleep()不会释放任何资源。

等待线程结束（join）和谦让（yield）：

public class joinTest {
    public volatile static int i=0;
    public static class AddThread extends Thread{
        public void run(){
            for(;i<10000000;i++);//相当于for(i=0;i<100000;i++);
        }
    }
    public static void main(String[] args) throws InterruptedException {
        AddThread t1=new AddThread();
        t1.start();
        t1.join();
        //主线程将等待t1线程执行完，再执行主线程；
        //如果没有join()，t1未执行完就切换到主线程，输出0-10000000的值；
        Thread.sleep(2);
        System.out.println(i);
    }
}

join内部是调用了wait:

while (isAlive()) {
wait(0);
}

join代码理解：

public class myJoinTest {
    public volatile static int i=0;
    public volatile static int j=0;
    public static class AddThread extends Thread{
        Thread b= new Thread(new Runnable(){
            public void run() {//B线程run方法；
                for(;j<20;j++){
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println("B线程"+"---:j="+j);
                }
                System.out.println("B线程结束!");
            }
        });
        public void run(){//A线程run方法；
            for(;i<20;i++){
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("A线程"+"---:i="+i);
                if(i==10){
                    try {
                        b.join();
                    /*
                    i<10,总共有三个线程争夺资源,当i=10时，线程A中调用了线程B的join()方法，此时CPU被A占用，引入B并被B占用，此后只有main线程和B争夺CPU执行权,
                    B结束后，才有A和main争夺执行权；
                    （当前线程中有其他线程执行join方法，则当前线程无权再争夺CPU，直到join调用者执行完，但join调用者在执行过程中仍会和别的线程争夺资源）
                    */    
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
            System.out.println("A线程结束!");
        }
    }
    public static void main(String[] args) throws InterruptedException {
        AddThread a = new AddThread();
        a.b.start();
        a.start();
        for(int k=0;k<50;k++){
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("main线程"+":k="+k);
        }
        System.out.println("main线程结束!");
    }
}

三、JDK并发包

　　使用重入锁可以替代synchronized、Object.wait()、Object.notify()；

重入锁：

　　重入锁使用java.util.concurrent.locks.ReentrantLock类实现。

import java.util.concurrent.locks.ReentrantLock;
public class ReenterLock implements Runnable{
    public static ReentrantLock lock=new ReentrantLock();
    //重入锁（reentrant-可重入）；
    public static int i=0;
    public void run() {
        for(int j=0;j<10;j++){
            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            lock.lock();
            //重入锁：在一个线程内，这种锁可以反复进入（一个线程连续两次获得同一把锁）。
            lock.lock();
            try{
            i++;
            }finally{
                lock.unlock();
                lock.unlock();
            }
            System.out.println(Thread.currentThread().getName()+" i="+i);
        }
    }
    public static void main(String[] args) throws InterruptedException {
        ReenterLock tl=new ReenterLock();
        Thread t1=new Thread(tl);
        Thread t2=new Thread(tl);
        t1.start();
        t2.start();
        for(int i=0;i<10;i++){
            Thread.sleep(200);
            System.out.println(Thread.currentThread().getName());
            t1.join();//join保证调用者在main线程之前执行完
            t2.join();
        }
        System.out.println(i);
    }
}

中断响应Page72：

请求锁时使用lockInterruptibly()替代lock()，这是一个可以对中断进行响应的锁申请，即在等待锁的过程中可以响应中断（死锁情况）。thread.interrupt()可以中断线程的锁等待，放弃在等待的锁申请，并且释放已经获得的锁（交叉死锁的另一个线程就可以获得被释放的锁，而继续执行下去）；

interrupt代码：

import java.util.concurrent.locks.ReentrantLock;
public class IntLock implements Runnable{
    public static ReentrantLock lock1=new ReentrantLock();
    public static ReentrantLock lock2=new ReentrantLock();
    int lock;
    public IntLock(int lock){
        this.lock=lock;
    }
    public void run() {
        try {
            if(lock==1){
                lock1.lockInterruptibly();//区别于lock();
                // （interruptibly-可中断）
                Thread.sleep(500);
                lock2.lockInterruptibly();
                System.out.println("lock==1");
            }else{
                lock2.lockInterruptibly();
                Thread.sleep(500);
                lock1.lockInterruptibly();
                System.out.println("lock!=1");
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally{
            if(lock1.isHeldByCurrentThread())//held-握住
                lock1.unlock();
            if(lock2.isHeldByCurrentThread())
                lock2.unlock();
            System.out.println(Thread.currentThread().getName()+"：线程退出！");
        }
    }
    public static void main(String[] args) throws InterruptedException {
        IntLock r1=new IntLock(1);
        IntLock r2=new IntLock(2);
        Thread t1=new Thread(r1);
        Thread t2=new Thread(r2);
        t1.start();
        t2.start();
        Thread.sleep(1000);
        t2.interrupt();
    }
}

限时等待申请锁：

使用tryLock(parm1,parm2)方法：

import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;
public class TimeLock implements Runnable{
    public static ReentrantLock lock=new ReentrantLock();
    public void run() {
        try {
            if(lock.tryLock(1, TimeUnit.SECONDS)){
    //当前线程请求锁lock，最多等待5秒，成功获得锁返回true，超过5秒没有得到锁就会返回false
                Thread.sleep(2000);
            }else{
                System.out.println(Thread.currentThread().getName()+" get lock failed");
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally{
            if(lock.isHeldByCurrentThread())
                lock.unlock();
        }
    }
    public static void main(String[] args) {
        TimeLock t=new TimeLock();
        Thread t1=new Thread(t);
        Thread t2=new Thread(t);
        t1.start();
        t2.start();
        //两者之一获得锁并会睡眠2s，另一个线程只会等待1s会返回false；
    }
}

公平锁与非公平锁：

ReentrantLock(boolean fair)

重入锁的Condition接口Page81：

await()

awaitUninterruptibly()

awaitNanos(Long nanosTimeout)

signal()

signalAll()

//await和signal
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

public class ReenterLockCondition implements Runnable {
    public static ReentrantLock lock=new ReentrantLock();
    public static Condition condition=lock.newCondition();
    @Override
    public void run() {
        try {
            lock.lock();
            condition.await();
            System.out.println("Thread is going on!");
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally{
            lock.unlock();
        }
    }
    public static void main(String[] args) throws InterruptedException {
        ReenterLockCondition t = new ReenterLockCondition();
        Thread t1 = new Thread(t);
        t1.start();
        Thread.sleep(1000);
        lock.lock();//?
        condition.signal();
        lock.unlock();//?
    }
}

　　阻塞队列源码中应用了重入锁和Condition对象。

信号量（Semaphore），可以指定多个线程同时访问一个资源。

public class SemapDemo implements Runnable{
    final Semaphore semp=new Semaphore(5);
    public void run() {
        try {
            semp.acquire();//申请信号量
            Thread.sleep(1000);
            System.out.println(Thread.currentThread().getName() + ":done!");
            semp.release();//释放信号量
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static void main(String[] args) {
        ExecutorService exec = Executors.newFixedThreadPool(20);
        final SemapDemo demo=new SemapDemo();
        for(int i=0;i<20;i++){
            exec.submit(demo);
        }
    }
}

读写锁ReadWriteLock（多操作次数远大于写操作次数时应用）Page87：

import java.util.Random;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

public class ReadWirterLockDemo {
    private static Lock lock=new ReentrantLock();//重入锁
    private static ReentrantReadWriteLock readWriteLock=new ReentrantReadWriteLock();//可重入读写锁
    private static Lock readLock=readWriteLock.readLock();
    private static Lock writeLock=readWriteLock.writeLock();
    private int value;
    public Object handleRead(Lock lock) throws InterruptedException {
        try {
            lock.lock();
            Thread.sleep(1000);
            return value;
        } finally{
            lock.unlock();
        }
    }
    public void handleWrite(Lock lock,int index) throws InterruptedException{
        try {
            lock.lock();
            Thread.sleep(1000);
            value = index;
        } finally{
            lock.unlock();
        }
    }
    public static void main(String[] args) {
        final ReadWirterLockDemo demo = new ReadWirterLockDemo();
        Runnable readRunnable=new Runnable(){
            public void run(){
                try {
                    demo.handleRead(readLock);
                    demo.handleRead(lock);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        };
        Runnable writeRunnable=new Runnable(){
            public void run(){
                try {
                    demo.handleWrite(writeLock, new Random().nextInt());
                    demo.handleWrite(lock, new Random().nextInt());
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        };
        for(int i=0;i<18;i++){
            new Thread(readRunnable).start();
        }
        for(int i=18;i<20;i++){
            new Thread(writeRunnable).start();
        }
    }
}

线程阻塞工具类：LockSupport

import java.util.concurrent.locks.LockSupport;
public class LockSupportDemo {
    public static Object u=new Object();
    static ChangeObjectThread t1=new ChangeObjectThread("线程t1");
    static ChangeObjectThread t2=new ChangeObjectThread("线程t2");
    public static class ChangeObjectThread extends Thread{
        public ChangeObjectThread(String name){
            super.setName(name);
        }
        public void run(){
            synchronized(u){
                System.out.println("in "+getName());
                LockSupport.park();
            /*    为当前线程准备一个许可，线程运行到该代码就会消费这个许可，并将许可变为
             * 不可用，线程阻塞（其他线程无法进入）。LockSupport.unpark(当前线程)可以使得许可变为可用。
             */
                System.out.println("代码片");
            }
        }
    }
    public static void main(String[] args) throws InterruptedException {
        t1.start();Thread.sleep(100);
        t2.start();
        LockSupport.unpark(t1);
        LockSupport.unpark(t2);
        t1.join();
        t2.join();
    }
}

LockSupport.park()支持中断影响，不会抛出InterruptedException异常。

 1 import java.util.concurrent.locks.LockSupport;
 2 public class LockSupportDemo {
 3     public static Object u=new Object();
 4     static ChangeObjectThread t1=new ChangeObjectThread("线程t1");
 5     static ChangeObjectThread t2=new ChangeObjectThread("线程t2");
 6     public static class ChangeObjectThread extends Thread{
 7         public ChangeObjectThread(String name){
 8             super.setName(name);
 9         }
10         public void run(){
11             synchronized(u){
12                 System.out.println("in "+getName());
13                 LockSupport.park();
14             /*    为当前线程准备一个许可，线程运行到该代码就会消费这个许可，并将许可变为
15              * 不可用，线程阻塞（其他线程无法进入）。LockSupport.unpark(当前线程)可以使得许可变为可用。
16              */
17                 if(Thread.interrupted()){
18                     System.out.println(getName()+" 被中断了！");
19                 }
20             }
21             System.out.println(getName()+"执行结束！");
22         }
23     }
24     public static void main(String[] args) throws InterruptedException {
25         t1.start();Thread.sleep(100);
26         t2.start();
27         t1.interrupt();
28         LockSupport.unpark(t2);
29     }
30 }

Page95

线程池的作用：避免系统频繁地创建和销毁线程，让创建的线程进行复用。

JDK提供了一套Executor框架用于线程控制（java.util.concurrent并发包核心类），ThreadPoolExecutor表示为一个线程池。

public ThreadPoolExecutor(

　　int corePoolSize,
　　int maximumPoolSize,
　　long keepAliveTime,
　　TimeUnit unit,
　　BlockingQueue<Runnable> workQueue)

①newFixedThreadPool(int capacity)有界线程池

 1 import java.util.concurrent.ExecutorService;
 2 import java.util.concurrent.Executors;
 3 import java.util.concurrent.Future;
 4 public class ThreadPoolDemo {
 5     public static class MyTask implements Runnable{
 6         public void run() {
 7             System.out.println(System.currentTimeMillis()+":Thread ID:"
 8                     +Thread.currentThread().getId());
 9             try {
10                 Thread.sleep(1000);
11             } catch (InterruptedException e) {
12                 e.printStackTrace();
13             }
14         }
15     }
16     public static void main(String[] args) {
17         MyTask task = new MyTask();
18         ExecutorService es = Executors.newFixedThreadPool(5);
19         for(int i=0;i<10;i++){
20             es.submit(task);
21         }
22     }
23 }

Page99

newFixedThreadPool(int capacity,ThreadFactory tf)

②newCachedThreadPool()；

newCachedThreadPool(ThreadFactory threadfactory)定制线程工厂；

public static class MyThreadFactory implements ThreadFactory{
        //根据需要自定义线程工厂类
        @Override
        public Thread newThread(Runnable r) {
            Thread thread=new Thread(r);
            thread.setName("定制池中的线程对象的名称：["+Math.random()+"]");
            return thread;
        }
    }
    @Test
    public void test(){
        MyThreadFactory threadFactory = new MyThreadFactory();
        ExecutorService es = Executors.newCachedThreadPool(threadFactory);
        for(int i=0;i<10;i++){
            es.execute(new Runnable(){
                @Override
                public void run() {
                    System.out.println("正在运行:"+Thread.currentThread().getName());
                }
            });
        }
    }

ThreadFactory

③newSingleThreadExecutor()单一线程池

newSingleThreadExecutor(ThreadFactory tf)

自定义线程创建：ThreadFactory

　　线程池中线程的创建来自于ThreadFactory接口。Thread newThread(Runnable r);

import java.util.concurrent.ExecutorService;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class ThreadFactoryTest {
    public static class MyTask implements Runnable{
        public void run() {
            System.out.println(Thread.currentThread().getName());
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
    public static void main(String[] args) throws InterruptedException {
        MyTask task = new MyTask();
        ExecutorService es =new ThreadPoolExecutor(5,5,
                0L,TimeUnit.MILLISECONDS,
                new SynchronousQueue<Runnable>(),
                new ThreadFactory(){
            public Thread newThread(Runnable r){
                Thread t=new Thread(r);
                t.setDaemon(true);
                //将所有线程都设为守护线程，当主线程退出后，将会强制销毁线程池；
                System.out.println("create "+t);
                return t;
            }
        });
        for(int i=0;i<5;i++){
            es.submit(task);
        }
        Thread.sleep(2000);
    }
}

线程池扩展：beforeExecute()、afterExecute()、terminated()

重写以上方法可以对线程池中执行的线程对象实现监控。

Page112

import java.util.concurrent.ExecutorService;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class ExtThreadPool {
    public static class MyTask implements Runnable{
        public String name;
        public MyTask(String name) {
            this.name = name;
        }
        public void run() {
            System.out.println("正在执行"+"Thread ID："+Thread.currentThread().getName()
                    +",Task Name="+name);
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
    public static void main(String[] args) throws InterruptedException {
        ExecutorService es=new ThreadPoolExecutor(5,5,0L,TimeUnit.MILLISECONDS,
                new LinkedBlockingQueue<Runnable>()){
            @Override
            protected void beforeExecute(Thread t, Runnable r) {
                System.out.println("准备执行："+((MyTask)r).name);
            }
            @Override
            protected void afterExecute(Runnable r, Throwable t) {
                System.out.println("执行完成："+((MyTask)r).name);
            }
            @Override
            protected void terminated() {
                System.out.println("线程池退出！");
            }
        };
        for(int i=0;i<5;i++){
            MyTask task = new MyTask("TASK-GEYM-"+i);
            es.execute(task);
            Thread.sleep(10);
        }
        es.shutdown();
    }
}

在线程池中寻找堆栈：

    public class DivTask implements Runnable{
        int a,b;
        public DivTask(int a,int b){
            this.a=a;
            this.b=b;
        }
        public void run() {
            double re=a/b;
            System.out.println(re);
        }
        public static void main(String[] args) throws InterruptedException, ExecutionException {
            ThreadPoolExecutor pools=new ThreadPoolExecutor(0,Integer.MAX_VALUE,
                    0L,TimeUnit.SECONDS,
                    new SynchronousQueue<Runnable>()){
                protected void beforeExecute(Thread t, Runnable r) {
                    System.out.println("准备执行："+t.getName());
                }
            };
            for(int i=0;i<5;i++){
        //        pools.submit(new DivTask(100, i));
        //        pools.execute(new DivTask(100, i));    //改用execute()，可以看到异常堆栈
                Future re = pools.submit(new DivTask(100, i));
                re.get();//或者获取Future,get方法可以抛出异常；
            }
        }
    }

Fork/Join框架，ForkJoinPool线程池Page117：

public class CountTask extends RecursiveTask<Long> {
    private static final int THRESHOLD=10000;
    private long start;
    private long end;
    public CountTask(long start, long end) {
        this.start = start;
        this.end = end;
    }
    protected Long compute() {
        long sum=0;
        boolean canCompute=(end-start)<THRESHOLD;
        if(canCompute){
            for(long i=start;i<=end;i++){
                sum+=i;
            }
        }else{
            long step=(start+end)/100;
            ArrayList<CountTask> subTasks=new ArrayList<CountTask>();
            long pos=start;
            for(int i=0;i<100;i++){
                long lastOne=pos+step;
                if(lastOne>end)lastOne=end;
                CountTask subTask=new CountTask(pos,lastOne);
                pos+=step+1;
                subTasks.add(subTask);
                subTask.fork();
            }
            for(CountTask t:subTasks){
                sum+=t.join();
            }
        }
        return sum;
    }
    public static void main(String[] args) {
        ForkJoinPool forkJoinPool = new ForkJoinPool();
        CountTask task=new CountTask(0,200000L);
        ForkJoinTask<Long> result=forkJoinPool.submit(task);
        try {
            long res=result.get();
            System.out.println("sum="+res);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }
}

Page119

JDK的并发容器：

程序就是“算法+数据结构”，容器类就是JDK准备好的线程数据结构（可以找到链表、HashMap、队列）；

并发集合：

Collections工具类具有将任意集合包装成线程安全的方法，多线程环境下的性能较低，使用java.util.concurrent包中的并发集合效率较高（优化了锁机制）；

public static Map map=Collections.synchronizedMap(new HashMap());

BlockingQueue：适合做数据共享的通道，当队列为空时，服务线程进行等待（Blocking-阻塞），当有新的消息进入队列后，自动将线程唤醒。（用于解耦生产者和消费者）

随机数据结构：跳表（SkipList）：

锁的优化及注意事项Page138

减少线程持有锁的时间，提高系统的吞吐量；

ThreadLocal的应用：线程的局部变量。

public class ThreadLocalTest {
    private static ThreadLocal<SimpleDateFormat> t1=new ThreadLocal<SimpleDateFormat>();
    public static class ParseDate implements Runnable{
        int i=0;
        public ParseDate(int i){
            this.i=i;
        }
        public void run() {
            try {
                if(t1.get()==null){
                    t1.set(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));
                }
                Date t=t1.get().parse("2015-03-29 19:29:"+i%60);
                System.out.println(i+":"+t);
            } catch (ParseException e) {
                e.printStackTrace();
            }
        }
    }
    public static void main(String[] args) {
        ExecutorService es = Executors.newFixedThreadPool(10);
        for(int i=0;i<1000;i++){
            es.execute(new ParseDate(i));
        }
    }
}

单例模式：

public class Singleton {
    private Singleton() {
        //构造函数设为私有，防止类外创建实例；
        System.out.println("Singleton is create!");
    }
    private static Singleton instance=new Singleton();
    //instance设为私有，类外无法修改，getInstance为静态的，instance也要设为静态的；
    public static Singleton getInstance(){
        return instance;
    }
}

不变模式：

public final class Product {//无法被继承，其方法也不会被重载而修改
    private final String no;//属性私有，不会被其他对象获取
    private final String name;
    //使用final修饰，其值可以在构造函数中初始化，不能再二次赋值
    private final double price;
    public Product(String no, String name, double price) {
        //构造函数必须全参，保证final变量赋初值
        super();
        this.no = no;
        this.name = name;
        this.price = price;
    }
    //没有setter方法，保证属性不会被修改
    public String getNo() {
        return no;
    }
    public String getName() {
        return name;
    }
    public double getPrice() {
        return price;
    }
}

JDK中的java.lang.String类和元数据包装类都是不变模式实现的（Boolean、Byte、Character、Double、Float、Integer、Long、Short）。

生产者-消费者模式：

import java.util.Random;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
final class PCData{
    private final int intData;
    public PCData(int intData) {
        super();
        this.intData = intData;
    }
    public PCData(String d){
        intData=Integer.valueOf(d);
    }
    public int getData(){
        return intData;
    }
    public String toString() {
        return "data:" + intData;
    }
}
public class Producer implements Runnable {
    private volatile boolean isRunning =true;
    private BlockingQueue<PCData> queue;
    private static AtomicInteger count=new AtomicInteger();
    private static final int SLEEPTIME=1000;
    public Producer(BlockingQueue<PCData> queue){
        this.queue=queue;
    }
    public void run() {
        PCData data=null;
        Random r=new Random();
        System.out.println("start producer id="+Thread.currentThread().getName());
            try {
                while(isRunning){
                Thread.sleep(r.nextInt(SLEEPTIME));
                data=new PCData(count.incrementAndGet());
                System.out.println(data+" is put into queue");
                if(!queue.offer(data,2,TimeUnit.SECONDS)){
                    System.err.println("failed to put data: "+data);
                    }
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
                Thread.currentThread().interrupt();
            }
        }
    public void stop(){
        isRunning=false;
    }
}

Producer

import java.text.MessageFormat;
import java.util.Random;
import java.util.concurrent.BlockingQueue;

public class Consumer implements Runnable{
    private BlockingQueue<PCData> queue;
    private static final int SLEEPTIME=1000;
    public Consumer(BlockingQueue<PCData> queue) {
        this.queue = queue;
    }
    public void run() {
        System.out.println("start Consumer id="+Thread.currentThread().getName());
        Random r=new Random();
        try{
            while(true){
                PCData data=queue.take();
                if(null!=data){
                    int re=data.getData()*data.getData();
                    System.out.println(MessageFormat.format("{0}*{1}={2}",data.getData(),data.getData(),re));
                    Thread.sleep(r.nextInt(SLEEPTIME));
                }
            }
        }catch(InterruptedException e){
            e.printStackTrace();
            Thread.currentThread().interrupt();
        }
    }
}

Consumer

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.LinkedBlockingQueue;

public class ProCusTest {
    public static void main(String[] args) throws InterruptedException {
        BlockingQueue<PCData> queue=new LinkedBlockingQueue<PCData>(10);
        Producer producer1 = new Producer(queue);
        Producer producer2 = new Producer(queue);
        Producer producer3= new Producer(queue);
        Consumer consumer1=new Consumer(queue);
        Consumer consumer2=new Consumer(queue);
        Consumer consumer3=new Consumer(queue);
        ExecutorService service = Executors.newCachedThreadPool();
        service.execute(producer1);
        service.execute(producer2);
        service.execute(producer3);
        service.execute(consumer1);
        service.execute(consumer2);
        service.execute(consumer3);
        Thread.sleep(10*1000);
        producer1.stop();
        producer2.stop();
        producer3.stop();
        Thread.sleep(3000);
        service.shutdown();
    }
}

mainTest

参考：http://ifeve.com/

posted @ 2018-01-16 10:29 笔记Next 阅读(213) 评论(0) 编辑收藏举报

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