///*******************************************************************
//*
//*   Projeto: POO em Java
//*
//*   Modulo: PilhaImpl.java
//*
//*   Objetivo: Implementa interface para o TAD Pilha.
//*
//*   Classes & Funcoes Exportadas: PilhaImpl
//*
//*   Versao Original: 1.0          Data: agosto 2001
//*
//*   Autor: Ismael H F Santos
//*
//*   Email: ismael@tecgraf.puc-rio.br
//*
//********************************************************************
//*
//*   Historico de Alteracoes:
//*
//*   DATA        AUTOR                  COMENTARIO
//*   ----        -----                  ----------
//*   xx/yy/00    ....                   ....
//*
//*******************************************************************/

public final class PilhaImpl implements PilhaInterf {
  private int _qtdObj, _maxCapacity, _incrCapacity;
  private Object[] _vet;

  PilhaImpl( int initialCapacity, int incrCapacity ) {
  	_vet = new Object[initialCapacity];
  	_qtdObj = 0;
  	_maxCapacity  = initialCapacity;
  	_incrCapacity = incrCapacity;
  }

  private void redim()  {
  	Object[] tmpVet = new Object[_maxCapacity + _incrCapacity ];
  	
  	for( int i = 0; i < _qtdObj; tmpVet[i] = _vet[i], i++ );
  	
  	_vet = tmpVet; 	
  	_maxCapacity += _incrCapacity;
  }

  public boolean isEmpty()
  {
  	return _qtdObj == 0;
  }

  public boolean isFull()
  {
  	return _qtdObj == _maxCapacity;
  }

  public void push( Object obj )
  {
  	if( isFull( ) )
  	  redim();
  	
  	_vet[_qtdObj++] = obj;
  }

  public Object pop( )
  {
    if( isEmpty( ) )
      return null;

  	Object temp = _vet[_qtdObj - 1];
  	
  	_vet[--_qtdObj] = null;
  	
  	return temp;
  }

  public Object top( )
  {
  	return _vet[_qtdObj - 1];
  }
}