### Question:
StringUtil { public static String trimToEmpty(String str) { return str == null ? EMPTY : 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 testTrimToEmpty() { Assert.assertEquals("", StringUtil.trimToEmpty("")); Assert.assertEquals("", StringUtil.trimToEmpty(null)); }