2011-Q2

gistfile1.java

public class Stack {
  int stack[];
  int unsigned nelem;
  
  public Stack(){ //Constructor
    nelem = 0;
    stack = new int[1000];
  }
  
  public synchronized void push(int d){
    
    stack[nelem] = d;
    nelem++;
    
    notify();
  }

  public synchronized int pop(){
   
    
    while( nelem == 0 ){
      wait();
    }
    
    /*
    following was wrong. nelem points where there is no element yet,ready to be pushed.
    int ret = stack[nelem];
    nelem--;
    */
    
    nelem--;
    int ret = stack[nelem];
    
    
    return ret;
  } 
  
}