displaysemaphore.java

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package concurrency.semaphore;

import java.awt.*;
import java.applet.*;
import concurrency.display.*;



/********************************************************/

class DisplaySemaphore extends Semaphore {

    NumberCanvas display_;
    int count_; //shadow value for display

    DisplaySemaphore(NumberCanvas t, int val) {
        super(val);
        count_=val;
        display_=t;
        display_.setcolor(Color.cyan);
        display_.setvalue(count_);
    }

    synchronized public void up() {
        super.up();
        ++count_;
        display_.setvalue(count_);
        try {Thread.sleep(200);}
        catch (InterruptedException e){Thread.currentThread().interrupt();} //reassert
    }

    synchronized public void down() throws InterruptedException{
       super.down();
       --count_;
       display_.setvalue(count_);
    }
}