code: public static CharPredicate range(final char a, final char b) {
      return new CharPredicate() {
        @Override public boolean isChar(char c) {
          return c >= a && c <= b;
        }
        @Override public String toString() {
          return "[" + a + '-' + b + "]";
        }
      };
    }
docs: A {@link CharPredicate} that returns true if the character is within the range of
  {@code [a, b]}.