code: public static boolean isValidJson (@Nonnull @WillClose final InputStream aIS, @Nonnull final Charset aFallbackCharset)
    {
      ValueEnforcer.notNull (aIS, "InputStream");
      ValueEnforcer.notNull (aFallbackCharset, "FallbackCharset");
  
      try
      {
        final Reader aReader = CharsetHelper.getReaderByBOM (aIS, aFallbackCharset);
        return isValidJson (aReader);
      }
      finally
      {
        StreamHelper.close (aIS);
      }
    }
docs: Check if the passed input stream can be resembled to valid Json content.
  This is accomplished by fully parsing the Json file each time the method is
  called. This consumes <b>less memory</b> than calling any of the
  <code>read...</code> methods and checking for a non-<code>null</code>
  result.
  
  @param aIS
  The input stream to use. Is automatically closed. May not be
  <code>null</code>.
  @param aFallbackCharset
  The charset to be used in case no BOM is present. May not be
  <code>null</code>.
  @return <code>true</code> if the Json is valid according to the version,
  <code>false</code> if not