StringUtils { public static String trim(String str) { return str == null ? null : str.trim(); }  static boolean isEmpty(String str); static boolean isContainEmpty(String... args); static boolean isBlank(String str); static String trimToNull(String str); static String trimToEmpty(String str); static String trim(String str); static boolean equals(String str1, String str2); static boolean equalsIgnoreCase(String str1, String str2); static boolean startsWith(String str, String prefix); static boolean startsWithIgnoreCase(String str, String prefix); static boolean isNumeric(String str); static String join(Collection<T> collection, String separator); static String join(Collection<T> collection, String separator,
                                StringFormatter<T> formatter); static final String EMPTY; }
@Test public void testTrim() { Assert.assertEquals("1234", StringUtils.trim("1234")); Assert.assertNull(StringUtils.trim(null)); }