Given a string that contains a single pair of parenthesis,
compute recursively a new string made of only of the parenthesis 
and their contents, so "xyz(abc)123" yields "(abc)". 
parenBit("xyz(abc)123") → "(abc)"
parenBit("x(hello)") → "(hello)"
parenBit("(xy)1") → "(xy)"

	public static String parenBit(String str) {
		if (str.charAt(0)=='('&& str.charAt(str.length()-1)==')')
			return str;
		if (str.charAt(0)=='(')
			return parenBit(str.substring(0, str.length()-1));
		return parenBit(str.substring(1));
		  
	}