### Question:
StringUtils { public static boolean isBlank(final 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 isNoneBlank(final CharSequence... css); static boolean isEmpty(final Object[] array); static boolean isBlank(final CharSequence cs);  }### Answer:
@Test public void testIsBlank() { Assert.assertTrue(StringUtils.isBlank(null)); Assert.assertTrue(StringUtils.isBlank("")); Assert.assertTrue(StringUtils.isBlank(" ")); Assert.assertFalse(StringUtils.isBlank("foobar")); Assert.assertFalse(StringUtils.isBlank("foo bar")); }