### Question:
StringUtils { public static boolean isBlank(CharSequence cs) { int strLen; if (cs == null || (strLen = cs.length()) == 0) { return true; } for (int i = 0; i < strLen; i++) { if (!Character.isWhitespace(cs.charAt(i))) { return false; } } return true; }  static boolean isEmpty(CharSequence cs); static boolean isNotEmpty(CharSequence cs); static boolean isBlank(CharSequence cs); static boolean isNotBlank(CharSequence cs); static String defaultString(final Object str); static String toString(Object o, String defaultVal); static String toString(Object o); static final String EMPTY; }### Answer:
@Test public void isBlank() { Assert.assertTrue(StringUtils.isBlank(null)); Assert.assertTrue(StringUtils.isBlank("")); Assert.assertTrue(StringUtils.isBlank(" ")); Assert.assertFalse(StringUtils.isBlank(" 1")); }