public static boolean isAllAlpha(String str){
  if (str == null)   return false;
  for (int i=str.length() - 1; i >= 0; i--) {
    if (!Character.isLetter(str.charAt(i)))     return false;
  }
  return true;
}

public static boolean isAllAlpha ( String str ) { if ( str == null ) return false ; for ( int i = str . length ( ) - 1 ; i >= 0 ; i -- ) { if ( ! Character . isLetter ( str . charAt ( i ) ) ) return false ; } return true ; }
returns true if all characters in the string are letters
