/*
Semaphore, shared data structures in Java
*/

class Semaphore
{
    private int val = 1;
    private int max;
    public Semaphore(int m) { val = max = m; }

    public synchronized void P()  // wait/proberen
    {
      try {
	if (val<1) wait();
	val--;
      } catch (InterruptedException iex)
	  {System.out.println(iex+", val="+val); }
    }
    public synchronized void V() // signal/verhogen
    {
	if (val<max) val++;
	notify();
    }
}

class Shared_Int
{
    private int val = 0; // value of counter
    public final int original;
    public Shared_Int(int v)  { val = original = v; }
    public synchronized int get() { return val; }
    public synchronized void set(int x) { val =x; }
    public synchronized void change(int dx) { val += dx; }
    public synchronized void reset() { val=original; }
}

class Shared_Bool
{
    private boolean val;
    public Shared_Bool(boolean b) { val=b; }
    public synchronized boolean get() { return val; }
    public synchronized void set(boolean b) { val=b; }
    public synchronized boolean toggle() { val = !val; return !val; }
}