### Question:
StringUtils { @SuppressWarnings("checkstyle:innerassignment") 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 Integer toInteger(StringBuilder value); static String toString(StringBuilder value); static Boolean toBoolean(StringBuilder value); static String fromInteger(Integer value); static String fromLong(Long value); static String fromString(String value); static String fromBoolean(Boolean value); static String fromBigInteger(BigInteger value); static String fromBigDecimal(BigDecimal value); static BigInteger toBigInteger(String s); static BigDecimal toBigDecimal(String s); static String fromFloat(Float value); static String fromDate(Date value); static String fromDouble(Double d); static String fromByte(Byte b); static String fromByteBuffer(ByteBuffer byteBuffer); static String replace(String originalString, String partToMatch, String replacement); static String join(String joiner, String... parts); static String lowerCase(String str); static String upperCase(String str); @SuppressWarnings("checkstyle:innerassignment") static boolean isBlank(final CharSequence cs); static final Charset UTF8; }### Answer:
@Test public void isBlankTest() { Assert.assertTrue(StringUtils.isBlank("")); Assert.assertTrue(StringUtils.isBlank(null)); Assert.assertFalse(StringUtils.isBlank("12334")); Assert.assertTrue(StringUtils.isBlank(" ")); }