semaphore.java

Reader Writer Problem to solve synchronization issues

/* $Id: Semaphore.java,v 1.2 1996/06/28 04:10:16 kmillik1 Exp $ */

/* $Log: Semaphore.java,v $
# Revision 1.2  1996/06/28  04:10:16  kmillik1
# Fixed $Log$ comment.
#
# Revision 1.1  1996/06/28  04:03:02  kmillik1
# Initial revision
#
*/

public class Semaphore extends Object {

  private int s;

  public Semaphore(int n) {
    s = n;
//	System.out.println("Semaphore");
  }
  
  public Semaphore() {
    this(0);
  }

  synchronized public void up() {
	int temp;
	temp=s;
	s=1;
//System.out.println("up value: "+s);
	if(temp==0){notify(); 
//	System.out.println("notified up value: "+s);
	};
  }

  synchronized public void down() {
    try {
      if (s > 0)
{
	s=0;
//	System.out.println("down value: "+s);
}
      else
{
//	System.out.print("down value: "+s);
//	System.out.println(" Waiting..");
	wait();
	s=0;
};

    }
    catch (InterruptedException e) {
      // add exception handler code here
    }
  }
}