java.text

Class Bidi

java.lang.Object

java.text.Bidi

public final class Bidi
extends Object

Implements the Unicode Bidirectional Algorithm.

Use a Bidi object to get the information on the position reordering of a bidirectional text, such as Arabic or Hebrew. The natural display ordering of horizontal text in these languages is from right to left, while they order numbers from left to right.

If the text contains multiple runs, the information of each run can be obtained from the run index. The level of any particular run indicates the direction of the text as well as the nesting level. Left-to-right runs have even levels while right-to-left runs have odd levels.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DIRECTION_DEFAULT_LEFT_TO_RIGHT Constant that indicates the default base level.
static int	DIRECTION_DEFAULT_RIGHT_TO_LEFT Constant that indicates the default base level.
static int	DIRECTION_LEFT_TO_RIGHT Constant that specifies the default base level as 0 (left-to-right).
static int	DIRECTION_RIGHT_TO_LEFT Constant that specifies the default base level as 1 (right-to-left).

Constructor Summary

Constructors

Constructor and Description
Bidi(AttributedCharacterIterator paragraph) Creates a Bidi object from the AttributedCharacterIterator of a paragraph text.
Bidi(char[] text, int textStart, byte[] embeddings, int embStart, int paragraphLength, int flags) Creates a Bidi object.
Bidi(String paragraph, int flags) Creates a Bidi object.

Method Summary

Modifier and Type	Method and Description
boolean	baseIsLeftToRight() Returns whether the base level is from left to right.
Bidi	createLineBidi(int lineStart, int lineLimit) Creates a new Bidi object containing the information of one line from this object.
int	getBaseLevel() Returns the base level.
int	getLength() Returns the length of the text.
int	getLevelAt(int offset) Returns the level of the given character.
int	getRunCount() Returns the number of runs in the text, at least 1.
int	getRunLevel(int run) Returns the level of the given run.
int	getRunLimit(int run) Returns the limit offset of the given run.
int	getRunStart(int run) Returns the start offset of the given run.
boolean	isLeftToRight() Returns true if the text is from left to right, that is, both the base direction and the text direction is from left to right.
boolean	isMixed() Returns true if the text direction is mixed.
boolean	isRightToLeft() Returns true if the text is from right to left, that is, both the base direction and the text direction is from right to left.
static void	reorderVisually(byte[] levels, int levelStart, Object[] objects, int objectStart, int count) Reorders a range of objects according to their specified levels.
static boolean	requiresBidi(char[] text, int start, int limit) Indicates whether a range of characters of a text requires a Bidi object to display properly.
String	toString() Returns a string containing a concise, human-readable description of this object.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

DIRECTION_DEFAULT_LEFT_TO_RIGHT

public static final int DIRECTION_DEFAULT_LEFT_TO_RIGHT

Constant that indicates the default base level. If there is no strong character, then set the paragraph level to 0 (left-to-right).

See Also:

Constant Field Values

DIRECTION_DEFAULT_RIGHT_TO_LEFT

public static final int DIRECTION_DEFAULT_RIGHT_TO_LEFT

Constant that indicates the default base level. If there is no strong character, then set the paragraph level to 1 (right-to-left).

See Also:

Constant Field Values

DIRECTION_LEFT_TO_RIGHT

public static final int DIRECTION_LEFT_TO_RIGHT

Constant that specifies the default base level as 0 (left-to-right).

See Also:

Constant Field Values

DIRECTION_RIGHT_TO_LEFT

public static final int DIRECTION_RIGHT_TO_LEFT

Constant that specifies the default base level as 1 (right-to-left).

See Also:

Constant Field Values

Constructor Detail

Bidi

public Bidi(AttributedCharacterIterator paragraph)

Creates a Bidi object from the AttributedCharacterIterator of a paragraph text. The RUN_DIRECTION attribute determines the base direction of the bidirectional text. If it is not specified explicitly, the algorithm uses DIRECTION_DEFAULT_LEFT_TO_RIGHT by default. The BIDI_EMBEDDING attribute specifies the level of embedding for each character. Values between -1 and -62 denote overrides at the level's absolute value, values from 1 to 62 indicate embeddings, and the 0 value indicates the level is calculated by the algorithm automatically. For the character with no BIDI_EMBEDDING attribute or with a improper attribute value, such as a null value, the algorithm treats its embedding level as 0. The NUMERIC_SHAPING attribute specifies the instance of NumericShaper used to convert European digits to other decimal digits before performing the bidi algorithm.

Parameters:

paragraph - the String containing the paragraph text to perform the algorithm.

Throws:

IllegalArgumentException - if paragraph == null

See Also:

TextAttribute.BIDI_EMBEDDING, TextAttribute.NUMERIC_SHAPING, TextAttribute.RUN_DIRECTION

Bidi

public Bidi(char[] text,
            int textStart,
            byte[] embeddings,
            int embStart,
            int paragraphLength,
            int flags)

Creates a Bidi object.

Parameters:

text - the char array of the paragraph text that is processed.

textStart - the index in text of the start of the paragraph.

embeddings - the embedding level array of the paragraph text, specifying the embedding level information for each character. Values between -1 and -61 denote overrides at the level's absolute value, values from 1 to 61 indicate embeddings, and the 0 value indicates the level is calculated by the algorithm automatically.

embStart - the index in embeddings of the start of the paragraph.

paragraphLength - the length of the text to perform the algorithm.

flags - indicates the base direction of the bidirectional text. It is expected that this will be one of the direction constant values defined in this class. An unknown value is treated as DIRECTION_DEFAULT_LEFT_TO_RIGHT.

Throws:

IllegalArgumentException - if textStart, embStart, or paragraphLength is negative; if text.length < textStart + paragraphLength or embeddings.length < embStart + paragraphLength.

See Also:

DIRECTION_LEFT_TO_RIGHT, DIRECTION_RIGHT_TO_LEFT, DIRECTION_DEFAULT_RIGHT_TO_LEFT, DIRECTION_DEFAULT_LEFT_TO_RIGHT

Bidi

public Bidi(String paragraph,
            int flags)

Creates a Bidi object.

Parameters:

paragraph - the string containing the paragraph text to perform the algorithm on.

flags - indicates the base direction of the bidirectional text. It is expected that this will be one of the direction constant values defined in this class. An unknown value is treated as DIRECTION_DEFAULT_LEFT_TO_RIGHT.

See Also:

DIRECTION_LEFT_TO_RIGHT, DIRECTION_RIGHT_TO_LEFT, DIRECTION_DEFAULT_RIGHT_TO_LEFT, DIRECTION_DEFAULT_LEFT_TO_RIGHT

Method Detail

baseIsLeftToRight

public boolean baseIsLeftToRight()

Returns whether the base level is from left to right.

Returns:

true if the base level is from left to right.

createLineBidi

public Bidi createLineBidi(int lineStart,
                           int lineLimit)

Creates a new Bidi object containing the information of one line from this object.

Parameters:

lineStart - the start offset of the line.

lineLimit - the limit of the line.

Returns:

the new line Bidi object. In this new object, the indices will range from 0 to (limit - start - 1).

Throws:

IllegalArgumentException - if lineStart < 0, lineLimit < 0, lineStart > lineLimit or if lineStart is greater than the length of this object's paragraph text.

getBaseLevel

public int getBaseLevel()

Returns the base level.

getLength

public int getLength()

Returns the length of the text.

getLevelAt

public int getLevelAt(int offset)

Returns the level of the given character.

getRunCount

public int getRunCount()

Returns the number of runs in the text, at least 1.

getRunLevel

public int getRunLevel(int run)

Returns the level of the given run.

getRunLimit

public int getRunLimit(int run)

Returns the limit offset of the given run.

getRunStart

public int getRunStart(int run)

Returns the start offset of the given run.

isLeftToRight

public boolean isLeftToRight()

Returns true if the text is from left to right, that is, both the base direction and the text direction is from left to right.

isMixed

public boolean isMixed()

Returns true if the text direction is mixed.

isRightToLeft

public boolean isRightToLeft()

Returns true if the text is from right to left, that is, both the base direction and the text direction is from right to left.

reorderVisually

public static void reorderVisually(byte[] levels,
                                   int levelStart,
                                   Object[] objects,
                                   int objectStart,
                                   int count)

Reorders a range of objects according to their specified levels. This is a convenience function that does not use a Bidi object. The range of objects at index from objectStart to objectStart + count will be reordered according to the range of levels at index from levelStart to levelStart + count.

Parameters:

levels - the level array, which is already determined.

levelStart - the start offset of the range of the levels.

objects - the object array to reorder.

objectStart - the start offset of the range of objects.

count - the count of the range of objects to reorder.

Throws:

IllegalArgumentException - if count, levelStart or objectStart is negative; if count > levels.length - levelStart or if count > objects.length - objectStart.

requiresBidi

public static boolean requiresBidi(char[] text,
                                   int start,
                                   int limit)

Indicates whether a range of characters of a text requires a Bidi object to display properly.

Parameters:

text - the char array of the text.

start - the start offset of the range of characters.

limit - the limit offset of the range of characters.

Returns:

true if the range of characters requires a Bidi object; false otherwise.

Throws:

IllegalArgumentException - if start or limit is negative; start > limit or limit is greater than the length of this object's paragraph text.

toString

public String toString()

Description copied from class: Object

Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression:

   getClass().getName() + '@' + Integer.toHexString(hashCode())

See Writing a useful toString method if you intend implementing your own toString method.

Overrides:

toString in class Object

Returns:

a printable representation of this object.