//An implementation of the StringStack interface that uses
// a (small) array as the actual data store.

public class mySS implements StringStack {
  
  String [] stuff;
  int nextSpot = 0;
  final static int MAX_SIZE = 10;
 
  mySS() {
    // Default constructor makes an array that can point at strings!
    stuff = new String[MAX_SIZE];
    
  }
  
  public void push( String element) {
    
    if( nextSpot == MAX_SIZE) {
      System.out.println("Error! Array is too small!"); 
    }
    
    stuff[ nextSpot ] = element;
    nextSpot = nextSpot + 1;
  }
  
  public String peek()
  {
    if (nextSpot == 0 ) {
      // nothing to return!
      return( null );
    }
       
    return( stuff[nextSpot -1 ] );
  }
  
  public String pop()
  {
    
    if (nextSpot == 0 ) {
      // nothing to return!
      return( null );
    }
    
    nextSpot = nextSpot -1;
    
    
    return( stuff[nextSpot] );

    
  }
  
  public int size() {
    return( nextSpot );
  }
  
  public boolean isEmpty() {
    
    return( nextSpot == 0);
    
//    if ( nextSpot == 0) {
//          return true;
//    } else {
//          return false;
 //   }
    
    
  } // end isEmpty
  
  
}