### Question:
StringUtil { public static String trim(String str) { return str == null ? null : str.trim(); }  static boolean equalsIgnoreCase(final CharSequence str1, final CharSequence str2); static boolean equals(String str1, String str2); static boolean isBlank(String str); static boolean isNotBlank(String str); static boolean isEmpty(String str); static boolean isNotEmpty(String str); static String trimToEmpty(String str); static String trim(String str); static String capitalize(String str); static final String EMPTY; }### Answer:
@Test public void testTrim() { Assert.assertNull(StringUtil.trim(null)); Assert.assertEquals("", StringUtil.trim("")); Assert.assertEquals("foo", StringUtil.trim("foo ")); }