IDN

AI-generated Key Takeaways

• The IDN class converts internationalized domain names (IDNs) between Unicode and ASCII Compatible Encoding (ACE) as defined in RFC 3490.

• It provides methods toASCII and toUnicode for converting between these formats, handling both individual labels and entire domain names.

• The constants ALLOW_UNASSIGNED and USE_STD3_ASCII_RULES allow for control over the conversion process.

• An IllegalArgumentException is thrown if the input to toASCII does not conform to RFC 3490.

public final class IDN extends Object

Converts internationalized domain names between Unicode and the ASCII Compatible Encoding (ACE) representation.

See RFC 3490 for full details.

Constant Summary

int	ALLOW_UNASSIGNED	When set, allows IDN to process unassigned unicode points.
int	USE_STD3_ASCII_RULES	When set, ASCII strings are checked against RFC 1122 and RFC 1123.

Public Method Summary

static String	toASCII(String input, int flags) Transform a Unicode String to ASCII Compatible Encoding String according to the algorithm defined in RFC 3490.
static String	toASCII(String input) Equivalent to toASCII(input, 0).
static String	toUnicode(String input, int flags) Translates a string from ASCII Compatible Encoding (ACE) to Unicode according to the algorithm defined in RFC 3490.
static String	toUnicode(String input) Equivalent to toUnicode(input, 0).

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Constants

public static final int ALLOW_UNASSIGNED

When set, allows IDN to process unassigned unicode points.

Constant Value: 1

public static final int USE_STD3_ASCII_RULES

When set, ASCII strings are checked against RFC 1122 and RFC 1123.

Constant Value: 2

Public Methods

public static String toASCII (String input, int flags)

Transform a Unicode String to ASCII Compatible Encoding String according to the algorithm defined in RFC 3490.

If the transformation fails (because the input is not a valid IDN), an exception will be thrown.

This method can handle either an individual label or an entire domain name. In the latter case, the separators are: U+002E (full stop), U+3002 (ideographic full stop), U+FF0E (fullwidth full stop), and U+FF61 (halfwidth ideographic full stop). All of these will become U+002E (full stop) in the result.

Parameters

input	the Unicode name
flags	0, ALLOW_UNASSIGNED, USE_STD3_ASCII_RULES, or ALLOW_UNASSIGNED | USE_STD3_ASCII_RULES

Returns

• the ACE name

Throws

IllegalArgumentException	if input does not conform to RFC 3490

public static String toASCII (String input)

Equivalent to toASCII(input, 0).

Parameters

input	the Unicode name

Returns

• the ACE name

Throws

IllegalArgumentException	if input does not conform to RFC 3490

public static String toUnicode (String input, int flags)

Translates a string from ASCII Compatible Encoding (ACE) to Unicode according to the algorithm defined in RFC 3490.

Unlike toASCII, this transformation cannot fail.

This method can handle either an individual label or an entire domain name. In the latter case, the separators are: U+002E (full stop), U+3002 (ideographic full stop), U+FF0E (fullwidth full stop), and U+FF61 (halfwidth ideographic full stop).

Parameters

input	the ACE name
flags	0, ALLOW_UNASSIGNED, USE_STD3_ASCII_RULES, or ALLOW_UNASSIGNED | USE_STD3_ASCII_RULES

Returns

• the Unicode name

public static String toUnicode (String input)

Equivalent to toUnicode(input, 0).

Parameters

input	the ACE name

Returns

• the Unicode name