src/main/java/com/github/fge/grappa/parsers/BaseParser.java
@Cached
    @DontLabel
    public Rule anyOf(final Characters characters)
    {
        Objects.requireNonNull(characters);
        if (!characters.isSubtractive() && characters.getChars().length == 1)
            return ch(characters.getChars()[0]);
        if (characters.equals(Characters.NONE))
            return NOTHING;
        return new AnyOfMatcher(characters);
    }
@Cached
    @DontLabel
    public Rule anyOf(final Characters characters)
    {
        Objects.requireNonNull(characters);
        if (!characters.isSubtractive() && characters.getChars().length == 1)
            return ch(characters.getChars()[0]);
        if (characters.equals(Characters.NONE))
            return NOTHING;
        return new AnyOfMatcher(characters);
    }
Match any given character among a set of characters

<p>Both {@link #anyOf(char[])} and {@link #anyOf(String)} ultimately
delegate to this method, which caches its resuls.</p>

@param characters the characters
@return a new rule