Uso de Stack y substring

import java.util.*;

class Ver {
 private Stack pila;
 Ver(){ pila=new Stack();}

 private void fillstack(String str)
 {
  for(int i=0;i          if (!str.substring(i,i+1).equals(" "))
                  pila.push(str.substring(i,i+1));
 }

 boolean palindro(String str)
 {
  boolean palindro=true;
  int i=0;
  fillstack(str);
  while( (palindro) & (str.length()>i))
  {
   if (!str.substring(i,i+1).equals(" "))
    if (str.substring(i,i+1).equals(pila.pop()))
     i++;
    else palindro=false;
   else i++;

  }
  return palindro;
 }
}

class test
{
 public static void main(String args[])
 {
  Ver Check = new Ver();

  String str1 = new String ("dabale arroz a la zorra el abad");
  String str2 = new String ("Esto no es una frase palindroma");

  System.out.println("Frase: " + str1 + ": ");
  if (Check.palindro(str1))
          System.out.println("palindroma");
  else System.out.println("no es palindroma");
  System.out.println("Frase: " + str2 + ": ");
  if (Check.palindro(str2))
          System.out.println("palindroma");
  else System.out.println("no es palindroma");
 }
}