Method is

src/main/java/org/apache/commons/lang3/CharRange.java:156–158

Constructs a CharRange over a single character. @param ch only character in this range. @return the new CharRange object. @since 2.5

(final char ch)

     * @since 2.5
     */
    public static CharRange is(final char ch) {
        return new CharRange(ch, ch, false);
    }

    /**
     * Constructs a {@link CharRange} over a set of characters.