JAVA多线程基础学习一：基础知识

class MyThread extends Thread{
    private static int num = 0;
     
    public MyThread(){
        num++;
    }
     
    @Override
    public void run() {
        System.out.println("主动创建的第"+num+"个线程");
    }
}

public class Test {
    public static void main(String[] args)  {
        MyThread thread = new MyThread();
        thread.start();
    }
}
class MyThread extends Thread{
    private static int num = 0;
    public MyThread(){
        num++;
    }
    @Override
    public void run() {
        System.out.println("主动创建的第"+num+"个线程");
    }
}

public class Test {
    public static void main(String[] args)  {
        System.out.println("主线程ID:"+Thread.currentThread().getId());
        MyThread thread1 = new MyThread("thread1");
        thread1.start();
        MyThread thread2 = new MyThread("thread2");
        thread2.run();
    }
}
 
 
class MyThread extends Thread{
    private String name;
     
    public MyThread(String name){
        this.name = name;
    }
     
    @Override
    public void run() {
        System.out.println("name:"+name+" 子线程ID:"+Thread.currentThread().getId());
    }
}

public class Test {
    public static void main(String[] args)  {
        System.out.println("主线程ID："+Thread.currentThread().getId());
        MyRunnable runnable = new MyRunnable();
        Thread thread = new Thread(runnable);
        thread.start();
    }
} 
class MyRunnable implements Runnable{
    public MyRunnable() {
    }

    @Override
    public void run() {
        System.out.println("子线程ID："+Thread.currentThread().getId());
    }
}

public void run() {
    if (target != null) {
        target.run();
    }
}

/**
* 有返回值的线程 
*/  
@SuppressWarnings("unchecked")  
public class Test {  
public static void main(String[] args) throws ExecutionException,  
    InterruptedException {  
   System.out.println("----程序开始运行----");  
   Date date1 = new Date();  
  
   int taskSize = 5;  
   // 创建一个线程池  
   ExecutorService pool = Executors.newFixedThreadPool(taskSize);  
   // 创建多个有返回值的任务  
   List<Future> list = new ArrayList<Future>();  
   for (int i = 0; i < taskSize; i++) {  
    Callable c = new MyCallable(i + " ");  
    // 执行任务并获取Future对象  
    Future f = pool.submit(c);  
    // System.out.println(">>>" + f.get().toString());  
    list.add(f);  
   }  
   // 关闭线程池  
   pool.shutdown();  
  
   // 获取所有并发任务的运行结果  
   for (Future f : list) {  
    // 从Future对象上获取任务的返回值，并输出到控制台  
    System.out.println(">>>" + f.get().toString());  
   }  
  
   Date date2 = new Date();  
   System.out.println("----程序结束运行----，程序运行时间【"  
     + (date2.getTime() - date1.getTime()) + "毫秒】");  
}  
}  
  
class MyCallable implements Callable<Object> {  
private String taskNum;  
  
MyCallable(String taskNum) {  
   this.taskNum = taskNum;  
}  
  
public Object call() throws Exception {  
   System.out.println(">>>" + taskNum + "任务启动");  
   Date dateTmp1 = new Date();  
   Thread.sleep(1000);  
   Date dateTmp2 = new Date();  
   long time = dateTmp2.getTime() - dateTmp1.getTime();  
   System.out.println(">>>" + taskNum + "任务终止");  
   return taskNum + "任务返回运行结果,当前任务时间【" + time + "毫秒】";  
}
}

public class Run1{
    public static void main(String[] args){                 
    System.out.println(Thread.currentThread().getName());
    }
}
```  

### sleep()方法
方法sleep()的作用是在指定的毫秒数内让当前“正在执行的线程”休眠（暂停执行）。这个“正在执行的线程”是指this.currentThread()返回的线程。

sleep方法有两个重载版本：
 ```java
sleep(long millis)     //参数为毫秒
sleep(long millis,int nanoseconds)    //第一参数为毫秒，第二个参数为纳秒

public class Test {
     
    private int i = 10;
    private Object object = new Object();
     
    public static void main(String[] args) throws IOException  {
        Test test = new Test();
        MyThread thread1 = test.new MyThread();
        MyThread thread2 = test.new MyThread();
        thread1.start();
        thread2.start();
    } 
     
     
    class MyThread extends Thread{
        @Override
        public void run() {
            synchronized (object) {
                i++;
                System.out.println("i:"+i);
                try {
                    System.out.println("线程"+Thread.currentThread().getName()+"进入睡眠状态");
                    Thread.currentThread().sleep(10000);
                } catch (InterruptedException e) {
                    // TODO: handle exception
                }
                System.out.println("线程"+Thread.currentThread().getName()+"睡眠结束");
                i++;
                System.out.println("i:"+i);
            }
        }
    }
}

// YieldTest.java的源码
class ThreadA extends Thread{
    public ThreadA(String name){ 
        super(name); 
    } 
    public synchronized void run(){ 
        for(int i=0; i <10; i++){ 
            System.out.printf("%s [%d]:%d\n", this.getName(), this.getPriority(), i); 
            // i整除4时，调用yield
            if (i%4 == 0)
                Thread.yield();
        } 
    } 
} 

public class YieldTest{ 
    public static void main(String[] args){ 
        ThreadA t1 = new ThreadA("t1"); 
        ThreadA t2 = new ThreadA("t2"); 
        t1.start(); 
        t2.start();
    } 
}

t1 [5]:0
t2 [5]:0
t1 [5]:1
t1 [5]:2
t1 [5]:3
t1 [5]:4
t1 [5]:5
t1 [5]:6
t1 [5]:7
t1 [5]:8
t1 [5]:9
t2 [5]:1
t2 [5]:2
t2 [5]:3
t2 [5]:4
t2 [5]:5
t2 [5]:6
t2 [5]:7
t2 [5]:8
t2 [5]:9

// YieldLockTest.java 的源码
public class YieldLockTest{ 

    private static Object obj = new Object();

    public static void main(String[] args){ 
        ThreadA t1 = new ThreadA("t1"); 
        ThreadA t2 = new ThreadA("t2"); 
        t1.start(); 
        t2.start();
    } 

    static class ThreadA extends Thread{
        public ThreadA(String name){ 
            super(name); 
        } 
        public void run(){ 
            // 获取obj对象的同步锁
            synchronized (obj) {
                for(int i=0; i <10; i++){ 
                    System.out.printf("%s [%d]:%d\n", this.getName(), this.getPriority(), i); 
                    // i整除4时，调用yield
                    if (i%4 == 0)
                        Thread.yield();
                }
            }
        } 
    } 
}

t1 [5]:0
t1 [5]:1
t1 [5]:2
t1 [5]:3
t1 [5]:4
t1 [5]:5
t1 [5]:6
t1 [5]:7
t1 [5]:8
t1 [5]:9
t2 [5]:0
t2 [5]:1
t2 [5]:2
t2 [5]:3
t2 [5]:4
t2 [5]:5
t2 [5]:6
t2 [5]:7
t2 [5]:8
t2 [5]:9

public class Test {
    public static void main(String[] args) {
        Thread t= Thread.currentThread();
        System.out.println(t.getName()+" "+t.getId());
    }
}

#### isAlive()方法  

方法isAlive()的功能是判断当前线程是否处于活动状态
代码：
```java
public class MyThread  extends Thread{
    @Override
    public void run() {
        System.out.println("run="+this.isAlive());
    }
}
public class RunTest {
    public static void main(String[] args) throws InterruptedException {
        MyThread myThread=new MyThread();
        System.out.println("begin =="+myThread.isAlive());
        myThread.start();
        System.out.println("end =="+myThread.isAlive());
    }
}

begin ==false
run=true
end ==false

public static void main(String[] args) throws InterruptedException {
        MyThread myThread=new MyThread();
        System.out.println("begin =="+myThread.isAlive());
        myThread.start();
        Thread.sleep(1000);
        System.out.println("end =="+myThread.isAlive());
    }

// 主线程
public class Father extends Thread {
    public void run() {
        Son s = new Son();
        s.start();
        s.join();
        ...
    }
}
// 子线程
public class Son extends Thread {
    public void run() {
        ...
    }
}

// JoinTest.java的源码
public class JoinTest{ 

    public static void main(String[] args){ 
        try {
            ThreadA t1 = new ThreadA("t1"); // 新建“线程t1”

            t1.start();                     // 启动“线程t1”
            t1.join();                        // 将“线程t1”加入到“主线程main”中，并且“主线程main()会等待它的完成”
            System.out.printf("%s finish\n", Thread.currentThread().getName()); 
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    } 

    static class ThreadA extends Thread{

        public ThreadA(String name){ 
            super(name); 
        } 
        public void run(){ 
            System.out.printf("%s start\n", this.getName()); 

            // 延时操作
            for(int i=0; i <1000000; i++)
               ;

            System.out.printf("%s finish\n", this.getName()); 
        } 
    } 
}

t1 start
t1 finish
main finish

public final void setPriority(int newPriority) {
        ThreadGroup g;
        checkAccess();
        if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
            throw new IllegalArgumentException();
        }
        if((g = getThreadGroup()) != null) {
            if (newPriority > g.getMaxPriority()) {
                newPriority = g.getMaxPriority();
            }
            setPriority0(priority = newPriority);
        }
    }

// SleepTest.java的源码
class ThreadA extends Thread{
    public ThreadA(String name){ 
        super(name); 
    } 
    public synchronized void run() { 
        try {
            for(int i=0; i <10; i++){ 
                System.out.printf("%s: %d\n", this.getName(), i); 
                // i能被4整除时，休眠100毫秒
                if (i%4 == 0)
                    Thread.sleep(100);
            } 
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    } 
} 

public class SleepTest{ 
    public static void main(String[] args){ 
        ThreadA t1 = new ThreadA("t1"); 
        t1.start(); 
    } 
}

t1: 0
t1: 1
t1: 2
t1: 3
t1: 4
t1: 5
t1: 6
t1: 7
t1: 8
t1: 9

synchronized(同步对象){
    需要同步的代码块;
}

/**
 一个场景,共同的资源
  生产者消费者模式 信号灯法
 wait() :等待，释放锁   sleep 不释放锁
 notify()/notifyAll():唤醒
  与 synchronized
 * @author Administrator
 *
 */
public class Movie {
    private String pic ;
    //信号灯
    //flag -->T 生产生产，消费者等待 ，生产完成后通知消费
    //flag -->F 消费者消费 生产者等待, 消费完成后通知生产
    private boolean flag =true;
    /**
     * 播放
     * @param pic
     */
    public synchronized void play(String pic){
        if(!flag){ //生产者等待
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        //开始生产
        try {
            Thread.sleep(500);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("生产了:"+pic);
        //生产完毕        
        this.pic =pic;
        //通知消费
        this.notify();
        //生产者停下
        this.flag =false;
    }
    
    public synchronized void watch(){
        if(flag){ //消费者等待
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        //开始消费
        try {
            Thread.sleep(200);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("消费了"+pic);
        //消费完毕
        //通知生产
        this.notifyAll();
        //消费停止
        this.flag=true;
    }
}

/**
 * 生产者
 * @author Administrator
 *
 */
public class Player implements Runnable {
    private Movie m ;
    
    public Player(Movie m) {
        super();
        this.m = m;
    }

    @Override
    public void run() {
        for(int i=0;i<20;i++){
            if(0==i%2){
                m.play("左青龙");
            }else{
                m.play("右白虎");
            }
        }
    }

}

public class Watcher implements Runnable {
    private Movie m ;
    
    public Watcher(Movie m) {
        super();
        this.m = m;
    }

    @Override
    public void run() {
        for(int i=0;i<20;i++){
            m.watch();
        }
    }

}

public class App {
    public static void main(String[] args) {
        //共同的资源
        Movie m = new Movie();
        
        //多线程
        Player p = new Player(m);
        Watcher w = new Watcher(m);
        
        new Thread(p).start();        
        new Thread(w).start();
    }
}

public class TestProduce {
    public static void main(String[] args) {
        SyncStack sStack = new SyncStack();
        Shengchan sc = new Shengchan(sStack);
        Xiaofei xf = new Xiaofei(sStack);
        sc.start();
        xf.start();
    }
}

class Mantou {
    int id;
    Mantou(int id){
        this.id=id;
    }
}

class SyncStack{
    int index=0;
    Mantou[] ms = new Mantou[10];
    
    public synchronized void push(Mantou m){
        while(index==ms.length){
            try {
                this.wait(); 
                //wait后，线程会将持有的锁释放。sleep是即使睡着也持有互斥锁。
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        this.notify(); //唤醒在当前对象等待池中等待的第一个线程。notifyAll叫醒所有在当前对象等待池中等待的所有线程。
        //如果不唤醒的话。以后这两个线程都会进入等待线程，没有人唤醒。
        ms[index]=m;
        index++;
    }
    public synchronized Mantou pop(){
        while(index==0){
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        this.notify();
        index--;
        return ms[index];
    }
}

class Shengchan extends Thread{
    SyncStack ss = null;
    
    public Shengchan(SyncStack ss) {
        this.ss=ss;
    }
    @Override
    public void run() {
        for (int i = 0; i < 20; i++) {
            System.out.println("造馒头："+i);
            Mantou m = new Mantou(i);
            ss.push(m);
        }
    }
}

class Xiaofei extends Thread{
    SyncStack ss = null;
    
    public Xiaofei(SyncStack ss) {
        this.ss=ss;
    }
    @Override
    public void run() {
        for (int i = 0; i < 20; i++) {
            Mantou m = ss.pop();
            System.out.println("吃馒头："+i);
            
        }
    }
}