Strings { public static String trim(final String s) { if (s == null) { return null; } else { return s.trim(); } } private  Strings(); static boolean isNull(final String s); static boolean isEmpty(final String s); static boolean isNotEmpty(final String s); static boolean isBlank(final String s); static String trim(final String s); static String trimToNull(final String s); static String trimToEmpty(final String s); static String toLowerCase(final String s);  }
@Test public void testTrim() { final String nullString = null; final String emptyString = ""; final String blankString = " "; final String string = " a "; assertThat(Strings.trim(nullString), is(nullValue())); assertThat(Strings.trim(emptyString), is("")); assertThat(Strings.trim(blankString), is("")); assertThat(Strings.trim(string), is("a")); }