/* Given a string, return recursively a "cleaned" string where adjacent chars * that are the same have been reduced to a single char. So "yyzzza" yields * "yza". */ public String stringClean(String str) { if(str.length() <= 1) return str; if(str.charAt(0) == str.charAt(1)) return stringClean(str.substring(1)); return str.charAt(0) + stringClean(str.substring(1)); }