/* 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)". */ public 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)); if(str.charAt(str.length() - 1) == ')') return parenBit(str.substring(1)); return parenBit(str.substring(1, str.length() - 1)); }