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线程之间的通信

1.1、线程之间的通信方法

多个线程在处理统一资源,但是任务却不同,这时候就需要线程间通信。
    等待/唤醒机制涉及的方法:
    1. wait():让线程处于冻结状态,被wait的线程会被存储到线程池中。
    2. notify():唤醒线程池中的一个线程(任何一个都有可能)。
    3. notifyAll():唤醒线程池中的所有线程。
  备注
    1、这些方法都必须定义在同步中,因为这些方法是用于操作线程状态的方法。
    2、必须要明确到底操作的是哪个锁上的线程!
    3、wait和sleep区别?
         1)wait可以指定时间也可以不指定。sleep必须指定时间。
         2)在同步中时,对CPU的执行权和锁的处理不同。
         wait:释放执行权,释放锁。
         sleep:释放执行权,不释放锁。
    为什么操作线程的方法wait、notify、notifyAll定义在了object类中,因为这些方法是监视器的方法,监视器其实就是锁。
锁可以是任意的对象,任意的对象调用的方式一定在object类中。

三、JDK 1.5新特性

一、Lock

Lock 实现提供了比使用 synchronized 方法和语句可获得的更广泛的锁定操作。此实现允许更灵活的结构,可以具有差别很大的属性,可以支持多个相关的 Condition 对象。

技术分享

public interface Condition

Condition 将 Object 监视器方法(waitnotify 和 notifyAll)分解成截然不同的对象,以便通过将这些对象与任意 Lock 实现组合使用,为每个对象提供多个等待 set(wait-set)。其中,Lock 替代了 synchronized 方法和语句的使用,Condition 替代了 Object 监视器方法的使用。

技术分享 

线程常用方法

No.
方法名称
类型
描述
1
public Thread(Runnable target)
构造
接收Runnable接口子类对象,实例化Thread对象
2
public Thread(Runnable target,String name)
构造
接收Runnable接口子类对象,实例化Thread对象,并设置线程名称
3
public Thread(String name)
构造
实例化Thread对象,并设置线程名称
4
public static Thread currentThread()
普通
返回目前正在执行的线程
5
public final String getName()
普通
返回线程的名称
6
public final int getPriority()
普通
发挥线程的优先级
7
public boolean isInterrupted()
普通
判断目前线程是否被中断,如果是,返回true,否则返回false
8
public final boolean isAlive()
普通
判断线程是否在活动,如果是,返回true,否则返回false
9
public final void join() throws InterruptedException
普通
等待线程死亡
10
public final synchronized void join(long millis) throws InterruptedException
普通
等待millis毫秒后,线程死亡
11
public void run()
普通
执行线程
12
public final void setName(String name)
普通
设定线程名称
13
public final void setPriority(int newPriority)
普通
设定线程的优先值
14
public static void sleep(long millis) throws InterruptedException
普通
使目前正在执行的线程休眠millis毫秒
15
public void start()
普通
开始执行线程
16
public static void yield()
普通
将目前正在执行的线程暂停,允许其它线程执行
17
public final void setDaemon(boolean on)
普通
将一个线程设置成后台运行
18
public final void setPriority(int newPriority)
普通
更改线程的优先级

 

 

 

 

 

五、守护线程和线程优先级

5.1、守护线程-后台资源

setDaemon
public final void setDaemon(boolean on)将该线程标记为守护线程或用户线程。

当正在运行的线程都是守护线程时,Java 虚拟机退出。 
该方法必须在启动线程前调用。

该方法首先调用该线程的 checkAccess 方法,且不带任何参数。这可能抛出 SecurityException(在当前线程中)。


参数:
on - 如果为 true,则将该线程标记为守护线程。 
抛出: 
IllegalThreadStateException - 如果该线程处于活动状态。 
SecurityException - 如果当前线程无法修改该线程。

当前台线程都结束时,后台线程自动结束。

 

5.2、线程优先级

 

setPriority
public final void setPriority(int newPriority)更改线程的优先级。 
首先调用线程的 checkAccess 方法,且不带任何参数。这可能抛出 SecurityException。

 

在其他情况下,线程优先级被设定为指定的 newPriority 和该线程的线程组的最大允许优先级相比较小的一个。

 


参数:
newPriority - 要为线程设定的优先级 
抛出: 
IllegalArgumentException - 如果优先级不在 MIN_PRIORITY 到 MAX_PRIORITY 范围内。

10-----1------------5

static int MAX_PRIORITY 
线程可以具有的最高优先级。
static int MIN_PRIORITY 
线程可以具有的最低优先级。
static int NORM_PRIORITY 
分配给线程的默认优先级。


SecurityException - 如果当前线程无法修改该线程。

getPriority
public final int getPriority()返回线程的优先级。

返回:
该线程的优先级。

 

 

 

六、join线程

作用:阻塞指定的线程等到另一个线程完成以后,再继续执行

package com.pb.thread.demo2;

public class MyThread implements Runnable {
    
    @Override
    public void run() {

        for(int x=0;x<10;x++){
            System.out.println(Thread.currentThread().getName()+"....."+x);
        }
    }

}
//=============
package com.pb.thread.demo2;

public class Demo {

    public static void main(String[] args) {
        
        MyThread my=new MyThread();
        Thread t1=new Thread(my);
        t1.setName("半路加入的线程");
        for(int x=0;x<10;x++){
            if(x==5){                
                try {
                    t1.start();
                    t1.join();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            
            }
            
            System.out.println(Thread.currentThread().getName()+"....."+x);
        }

    }

}

结果:

main.....0
main.....1
main.....2
main.....3
main.....4
半路加入的线程.....0
半路加入的线程.....1
半路加入的线程.....2
半路加入的线程.....3
半路加入的线程.....4
半路加入的线程.....5
半路加入的线程.....6
半路加入的线程.....7
半路加入的线程.....8
半路加入的线程.....9
main.....5
main.....6
main.....7
main.....8
main.....9

或者

package com.pb.thread.demo2;

public class Test {

    public static void main(String[] args) {

        for(int x=0;x<10;x++){
            if(x==5){
            
                try {
                    Thread t1=new Thread(new MyThread(),"半路加入的线程");
                    t1.start();
                    t1.join();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            
            System.out.println(Thread.currentThread().getName()+"....."+x);
        }

    }

}

 

七、yield

 

yield
public static void yield()暂停当前正在执行的线程对象,并执行其他线程。

 

package com.pb.thread.demo2;

public class MyThread implements Runnable {
    
    @Override
    public void run() {

        for(int x=0;x<10;x++){
            
            System.out.println(Thread.currentThread().getName()+"....."+x);
            Thread.yield();
        }
    }

}
//===========
package com.pb.thread.demo2;

public class Test {

    public static void main(String[] args) {
        new Thread(new MyThread(),"线程一").start();
        new Thread(new MyThread(),"线程二").start();

    }

}

 

 八、停止线程

 

 开启多线程,运行代码通常是循环结构

只要控制住循环,就可以让run方法结束。也就是线程结束。

 

package com.pb.thread.demo4;

public class StopThread implements Runnable {
private boolean flag=true;
    @Override
    public void run() {
        while(flag){
            System.out.println(Thread.currentThread().getName()+"......run");
        }

    }
    public void setChangeFlag(){
        this.flag=false;
    }
    public static void main(String[] args) {
         StopThread st=new StopThread();
         Thread t1=new Thread(st);
         Thread t2=new Thread(st);
         t1.start();
         t2.start();
         int num=0;
         while(true){
             if(num++==60){
                 st.setChangeFlag();
                 break;
                 
             }
             System.out.println(Thread.currentThread().getName()+"===="+num);
         }
    }

}

 

 

 

 

interrupt

 

public void interrupt()

如果线程在调用 Object 类的 wait()wait(long) 或 wait(long, int) 方法,或者该类的join()join(long)join(long, int)sleep(long) 或 sleep(long, int) 方法过程中受阻,则其中断状态将被清除,它还将收到一个 InterruptedException。  

package com.pb.thread.demo4;

public class StopThread implements Runnable {
    private boolean flag = true;

    @Override
    public synchronized void run() {
        while (flag) {
            try {
                wait();
            } catch (InterruptedException e) {
                // e.printStackTrace();
                System.out.println(Thread.currentThread().getName() + "......Exception");
                flag = false; //设置标识为false
            }
            System.out.println(Thread.currentThread().getName() + "......run");
        }

    }

    public void setChangeFlag() {
        this.flag = false;
    }

    public static void main(String[] args) {
        StopThread st = new StopThread();
        Thread t1 = new Thread(st);
        Thread t2 = new Thread(st);
        t1.start();
        t2.start();
        int num = 0;
        while (true) {
            if (num++ == 60) {
                //中断状态也就是冻结状态,回到运行状态
                t1.interrupt();
                t2.interrupt();
                break;

            }
            System.out.println(Thread.currentThread().getName() + "====" + num);
        }
        System.out.println("over");
    }

}
main====1
main====2
main====3
main====4
main====5
main====6
main====7
main====8
main====9
main====10
main====11
main====12
main====13
main====14
main====15
main====16
main====17
main====18
main====19
main====20
main====21
main====22
main====23
main====24
main====25
main====26
main====27
main====28
main====29
main====30
main====31
main====32
main====33
main====34
main====35
main====36
main====37
main====38
main====39
main====40
main====41
main====42
main====43
main====44
main====45
main====46
main====47
main====48
main====49
main====50
main====51
main====52
main====53
main====54
main====55
main====56
main====57
main====58
main====59
main====60
over
Thread-1......Exception
Thread-1......run
Thread-0......Exception
Thread-0......run

 

九、sleep();

 

sleep

public static void sleep(long millis) throws InterruptedException

在指定的毫秒数内让当前正在执行的线程休眠(暂停执行),此操作受到系统计时器和调度程序精度和准确性的影响。该线程不丢失任何监视器的所属权。

 

 

参数:

millis - 以毫秒为单位的休眠时间。

抛出:

InterruptedException - 如果任何线程中断了当前线程。当抛出该异常时,当前线程的中断状态 被清除。

 

 十、toString

toString

public String toString()

返回该线程的字符串表示形式,包括线程名称、优先级和线程组。

 

覆盖:
类 Object 中的 toString
返回:
该线程的字符串表示形式。

 

package com.pb.thread.demo4;

public class StopThread implements Runnable {
    private boolean flag = true;

    @Override
    public synchronized void run() {
        while (flag) {        
            System.out.println(Thread.currentThread().toString()+ "......run");
        }

    }

    public void setChangeFlag() {
        this.flag = false;
    }

    public static void main(String[] args) {
        StopThread st = new StopThread();
        Thread t1 = new Thread(st);
        Thread t2 = new Thread(st);
        t1.start();
        t2.start();
        int num = 0;
        while (true) {
            if (num++ == 60) {
                st.setChangeFlag();
                break;
            }
            System.out.println(Thread.currentThread().toString()+ "====" + num);
        }
        System.out.println("over");
    }

}
Thread[Thread-0,5,main]......run
Thread[main,5,main]====1
Thread[Thread-0,5,main]......run
Thread[main,5,main]====2
Thread[Thread-0,5,main]......run
Thread[main,5,main]====3
Thread[Thread-0,5,main]......run
Thread[main,5,main]====4
Thread[main,5,main]====5
Thread[main,5,main]====6
Thread[main,5,main]====7
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[main,5,main]====8
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[main,5,main]====9
Thread[Thread-0,5,main]......run
Thread[main,5,main]====10
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[main,5,main]====11
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[main,5,main]====12
Thread[main,5,main]====13
Thread[main,5,main]====14
Thread[main,5,main]====15
Thread[main,5,main]====16
Thread[Thread-0,5,main]......run
Thread[main,5,main]====17
Thread[main,5,main]====18
Thread[main,5,main]====19
Thread[main,5,main]====20
Thread[main,5,main]====21
Thread[main,5,main]====22
Thread[main,5,main]====23
Thread[main,5,main]====24
Thread[main,5,main]====25
Thread[main,5,main]====26
Thread[main,5,main]====27
Thread[main,5,main]====28
Thread[main,5,main]====29
Thread[main,5,main]====30
Thread[main,5,main]====31
Thread[main,5,main]====32
Thread[main,5,main]====33
Thread[main,5,main]====34
Thread[main,5,main]====35
Thread[main,5,main]====36
Thread[main,5,main]====37
Thread[main,5,main]====38
Thread[main,5,main]====39
Thread[main,5,main]====40
Thread[main,5,main]====41
Thread[main,5,main]====42
Thread[main,5,main]====43
Thread[main,5,main]====44
Thread[main,5,main]====45
Thread[main,5,main]====46
Thread[main,5,main]====47
Thread[main,5,main]====48
Thread[main,5,main]====49
Thread[main,5,main]====50
Thread[main,5,main]====51
Thread[main,5,main]====52
Thread[main,5,main]====53
Thread[main,5,main]====54
Thread[main,5,main]====55
Thread[main,5,main]====56
Thread[main,5,main]====57
Thread[main,5,main]====58
Thread[main,5,main]====59
Thread[main,5,main]====60
over
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[main,5,main]====1
Thread[Thread-0,5,main]......run
Thread[main,5,main]====2
Thread[Thread-0,5,main]......run
Thread[main,5,main]====3
Thread[Thread-0,5,main]......run
Thread[main,5,main]====4
Thread[main,5,main]====5
Thread[main,5,main]====6
Thread[main,5,main]====7
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[main,5,main]====8
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[main,5,main]====9
Thread[Thread-0,5,main]......run
Thread[main,5,main]====10
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[main,5,main]====11
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[Thread-0,5,main]......run
Thread[main,5,main]====12
Thread[main,5,main]====13
Thread[main,5,main]====14
Thread[main,5,main]====15
Thread[main,5,main]====16
Thread[Thread-0,5,main]......run
Thread[main,5,main]====17
Thread[main,5,main]====18
Thread[main,5,main]====19
Thread[main,5,main]====20
Thread[main,5,main]====21
Thread[main,5,main]====22
Thread[main,5,main]====23
Thread[main,5,main]====24
Thread[main,5,main]====25
Thread[main,5,main]====26
Thread[main,5,main]====27
Thread[main,5,main]====28
Thread[main,5,main]====29
Thread[main,5,main]====30
Thread[main,5,main]====31
Thread[main,5,main]====32
Thread[main,5,main]====33
Thread[main,5,main]====34
Thread[main,5,main]====35
Thread[main,5,main]====36
Thread[main,5,main]====37
Thread[main,5,main]====38
Thread[main,5,main]====39
Thread[main,5,main]====40
Thread[main,5,main]====41
Thread[main,5,main]====42
Thread[main,5,main]====43
Thread[main,5,main]====44
Thread[main,5,main]====45
Thread[main,5,main]====46
Thread[main,5,main]====47
Thread[main,5,main]====48
Thread[main,5,main]====49
Thread[main,5,main]====50
Thread[main,5,main]====51
Thread[main,5,main]====52
Thread[main,5,main]====53
Thread[main,5,main]====54
Thread[main,5,main]====55
Thread[main,5,main]====56
Thread[main,5,main]====57
Thread[main,5,main]====58
Thread[main,5,main]====59
Thread[main,5,main]====60
over
Thread[Thread-0,5,main]......run

 十一、匿名内部类实现多线程

 

package com.pb.thread.demo4;
/*
 * 匿名内部类实现多线程
 */
public class ThreadTest {

    public static void main(String[] args) {
        //线程对象
        new Thread(){
            public void run(){
                for (int x = 0; x < 100; x++) {
                    System.out.println(Thread.currentThread().getName()+".........."+x);
                }
            }
        }.start();
        //Runnable 接口
        Runnable r=new Runnable(){
            public void run(){
                for (int x = 0; x < 100; x++) {
                    System.out.println(Thread.currentThread().getName()+".........."+x);
                }
            }
        };
        //启动线程
        new Thread(r).start();
    }

}

 

 

线程之间的通信