@SuppressWarnings("checkstyle:WhitespaceAround")
    public static String[] split(final String str, String separatorChars) {
        if (str == null) {
            return null;
        }
        if (str.length() == 0) {
            return new String[0];
        }
        if (separatorChars == null) {
            separatorChars = " +";
        }
        return str.split(separatorChars);
    }
@Test
    void testSplit() {
        assertNull(StringUtils.split(null, ","));
        assertArrayEquals(new String[0], StringUtils.split("", ","));
        assertArrayEquals(new String[] {"ab", "cd", "ef"}, StringUtils.split("ab cd ef", null));
        assertArrayEquals(new String[] {"ab", "cd", "ef"}, StringUtils.split("ab   cd ef", null));
        assertArrayEquals(new String[] {"ab", "cd", "ef"}, StringUtils.split("ab:cd:ef", ":"));
    }