StringUtils { public static final boolean isEmpty(String str) { return str == null || str.length() == 0; }  static final boolean isEmpty(String str); static final boolean isNotEmpty(String str); static final String join(String[] array, String separator); static final String join(Collection<String> list, String separator); static final String normalizeSpace(String str); static final String trimAll(String str);  }
@Test public void testIsEmpty() { Assert.assertTrue(StringUtils.isEmpty("")); Assert.assertTrue(StringUtils.isEmpty(null)); Assert.assertFalse(StringUtils.isEmpty("foo")); }