Method isLowerCase

guava/src/com/google/common/base/Ascii.java:503–507

Indicates whether {@code c} is one of the twenty-six lowercase ASCII alphabetic characters between {@code 'a'} and {@code 'z'} inclusive. All others (including non-ASCII characters) return {@code false}.

(char c)

   * return {@code false}.
   */
  public static boolean isLowerCase(char c) {
    // Note: This was benchmarked against the alternate expression "(char)(c - 'a') < 26" (Nov '13)
    // and found to perform at least as well, or better.
    return (c >= 'a') && (c <= 'z');
  }

  /**
   * Indicates whether {@code c} is one of the twenty-six uppercase ASCII alphabetic characters