/** * Returns an optional charset for the value of the charset parameter if it is specified. * * @throws IllegalStateException if multiple charset values have been set for this media type * @throws IllegalCharsetNameException if a charset value is present, but illegal * @throws UnsupportedCharsetException if a charset value is present, but no support is available * in this instance of the Java virtual machine */ public Optional<Charset> charset() { // racy single-check idiom, this is safe because Optional is immutable. Optional<Charset> local = parsedCharset; if (local == null) { String value = null; local = Optional.absent(); for (String currentValue : parameters.get(CHARSET_ATTRIBUTE)) { if (value == null) { value = currentValue; local = Optional.of(Charset.forName(value)); } else if (!value.equals(currentValue)) { throw new IllegalStateException( "Multiple charset values defined: " + value + ", " + currentValue); } } parsedCharset = local; } return local; }