public String moveForward(){
  Check.isTrue(currentIndex < history.size() - 1,"currentIndex < history.size() - 1");
  currentIndex++;
  return history.get(currentIndex);
}

public String moveForward ( ) { Check . isTrue ( currentIndex < history . size ( ) - 1 , "currentIndex < history.size() - 1" ) ; currentIndex ++ ; return history . get ( currentIndex ) ; }
return the next url in the list ( relative to the current position ) and moves the index back to make this the now current position .
