// COM3336 Operating Systems
// Homework 1 part 2
// John Sung
// Started: 10/9/1999
//
//



// the mutex class to keep track of the number of spawned threads
// so that the thread that spawned the threads can wait for all of
// the spawned threads are done.
public class ThreadMutex
{

	 ///////////////////////////////////////////
	 // private variables

	 // the counter to count the number of threads.
	 private int ThreadCount;

	 // constructor for this class
	 ThreadMutex(int initialValue)
	 {
		  // set the initial value for this mutex.
		  // usually 0.
		  ThreadCount = initialValue;
	 }

	 // change the thread count number, threadCount can be a negative number.
	 public synchronized void changeThreadCount(int threadCount)
	 {

		  // add the threadCount to the running thread count.
		  ThreadCount += threadCount;
		  		  
		  // if the threadcount is less than zero then print some kind of
		  // error and just reset the thread count.
		  if (ThreadCount < 0)
				{
					 System.out.println("Warning, Thread Count less than zero");
					 System.out.print("Thread count = ");
					 System.out.println(ThreadCount);
					 ThreadCount = 0;
				}
	 }
	 	 
	 // checking to see if the threads have finished
	 public  boolean areThreadsFinished()
	 {
		  // if the thread count is zero then return true,
		  // else return false.
		  if (ThreadCount == 0)
				return true;

		  else
				return false;
	 }

}