如何从正在运行的实例中获取值

Question

Hi Could some one Kindly help here. 1)Where i am maintaining one flag for running application if true always my application will run continuously.

2. If flag is false have to stop running application.

Note:- Parameters are considering as run time arguments.

How second process will change first process value.

Exe:-

class Sample{


    public void run(boolean runstate)
    {
    
    while(runstate){
    //do something
    }
    
    }
    
    }

Answer 1

You need to execute "run()" in a separate thread from the main process. Use this code to break the loop:

class Sample{

    private boolean runstate;

    public void run(boolean runstate) // this runs in a separate thread...
    {
        this.runstate = runstate;
        
        while(runstate)
        {
            //do something
        }
    
    }
    
    public void setRunstate(boolean newrunstate)
    {
        this.runstate = newrunstate;
    }
    
}

class Other{

    void foo(Sample sample) // this runs in a separate thread...
    {
        sample.setRunstate(false);
    }

}

Answer 2

Naturally, there have to be 2 threads - one threads runs the above code, the other listens for a request to set the flag. Also, the flag has to be accessible to both objects running in the 2 threads.

Here is an example code that starts 2 threads. One keeps working till FLAG has true . The other thread sleeps for 200ms and then sets FLAG to false . The other threads detects this and stops.

package practice.soflow.concurrent;

import java.util.concurrent.atomic.AtomicReference;

public class FlagSetting{
    private static AtomicReference<Boolean> FLAG = new AtomicReference<Boolean>( Boolean.TRUE );

    public static void main( String[] args ){
        /* Main activity thread. This depends upon the status of FLAG. */
        new Thread( () -> {
            while( FLAG.get() ){
                //do something
                System.out.println( "Hi" );
            }
        } ).start();

        /* The controller thread. This changes the value of FLAG.
         * In this example, it will set it to false after 2 s; */
        new Thread( () -> {
            try{
                Thread.sleep( 200 );
            }
            catch( InterruptedException e ){}

            FLAG.set( Boolean.FALSE );
        } ).start();

    }
}