### Question:
StringValidateEncodeUtils { public static boolean validAlphanumericString(String alphNumString) { if (alphNumString == null) return false; Matcher m = VALID_CHARACTERS_FOR_ALPHANUMERIC_STRING_PATTERN.matcher(alphNumString); return m.matches(); } private  StringValidateEncodeUtils(); static boolean validSingleLineString(String singleLineString); @SuppressWarnings({"SimplifiableIfStatement"}) static boolean validPath(String path); @SuppressWarnings({"SimplifiableIfStatement"}) static boolean validFilePath(String path); @SuppressWarnings({"SimplifiableIfStatement"}) static boolean validUriString(String uri); static boolean validIdString(String id); static boolean containsAngleBracketCharacters(String string); static boolean containsAmpersandCharacters(String string); static boolean containsBackslashCharacters(String string); static boolean validDecimalNumber(String number); @SuppressWarnings({"SimplifiableIfStatement"}) static boolean validBooleanString(String boolString); static boolean validAlphanumericString(String alphNumString); static boolean validAlphanumericStringConstrainedSet(String alphNumString, String[] constrainedSet,
      boolean ignoreCase); @SuppressWarnings({"UnnecessaryContinue"}) static boolean descendOnlyFilePath(String path); static boolean validPercentHexOctetsString(String percentHexOctetsString); static String unicodeCodePoint2PercentHexString(int codePoint, String charsetName); final static String CHARACTER_ENCODING_UTF_8; }### Answer:
@Test public void testValidAlphanumericString() { assertTrue(StringValidateEncodeUtils.validAlphanumericString("true")); assertTrue(StringValidateEncodeUtils.validAlphanumericString("abcdefghigklmnopqrstuvwxyz")); assertTrue(StringValidateEncodeUtils.validAlphanumericString("ABCDEFGHIJKLMNOPQRSTUVWXYZ")); assertTrue(StringValidateEncodeUtils.validAlphanumericString("0123456789")); assertTrue(StringValidateEncodeUtils.validAlphanumericString("1aB")); assertFalse(StringValidateEncodeUtils.validAlphanumericString("1&aB")); assertFalse(StringValidateEncodeUtils.validAlphanumericString("1 aB")); }