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2020-01-06 11:14
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Java线程中synchronized 使用?

挂起方法hangUP,如果不加synchronized,恢复后,后面的println为什么不能执行。
public class Example8_12{

public static void main(String args[]){
    MyThread thread=new MyThread();
    thread.setName("张三");
    thread.start();
    while(thread.getStop()==false){}
    System.out.println("我是主线程,负责恢复"+thread.getName()+"线程");
    thread.restart();
  }

}

class MyThread extends Thread{

int number=0;
boolean stop=false;
boolean getStop(){
return stop;
}
public void run(){
    while(true){
number++;
System.out.println(Thread.currentThread().getName()+"的number="+number);
if(number==3){
      try{  System.out.println(Thread.currentThread().getName()+"被挂起");
    stop=true;
    hangUP();
    System.out.println(Thread.currentThread().getName()+"恢复执行");
     }
     catch(Exception e){}
}
try{Thread.sleep(1000);}
catch(Exception e){}
    }

}

public synchronized void hangUP() throws InterruptedException{
wait();

}

public synchronized void restart(){
notifyAll();

}

}

图片说明

不加synchronized:

public class Example8_12{

public static void main(String args[]){
MyThread thread=new MyThread();
thread.setName("张三");
thread.start();
while(thread.getStop()==false){}
System.out.println("我是主线程,负责恢复"+thread.getName()+"线程");
thread.restart();
  }

}
class MyThread extends Thread{

int number=0;
boolean stop=false;
boolean getStop(){
return stop;
}
public void run(){
    while(true){
number++;
System.out.println(Thread.currentThread().getName()+"的number="+number);
if(number==3){
      try{  System.out.println(Thread.currentThread().getName()+"被挂起");
    stop=true;
    hangUP();
    System.out.println(Thread.currentThread().getName()+"恢复执行");
     }
     catch(Exception e){}
}
try{Thread.sleep(1000);}
catch(Exception e){}
    }

}

public void hangUP() throws InterruptedException{
wait();

}

public synchronized void restart(){
notifyAll();

}

}

图片说明


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