Given a string, return true if it is a nesting of zero or more pairs of parenthesis, like "(())" or "((()))".

Given a string, return true if it is a nesting of zero or more pairs of parenthesis, like "(())" or "((()))". Suggestion: check the first and last chars, and then recur on what's inside them.

nestParen("(())") → true
nestParen("((()))") → true
nestParen("(((x))") → false

public boolean nestParen(String str) {

  if(str==null || str.length()==0)

  {

    return true;

  }

  else if(str.charAt(0)=='(' && str.charAt(str.length()-1)==')')

  {

    return nestParen(str.substring(1,str.length()-1));

  }

  else

  {

    return false;

  }

}