java.text
Class Bidi

java.lang.Object
  java.text.Bidi

public final class Bidi
extends Object

Bidi is the class providing the bidirectional algorithm. The algorithm is defined in the Unicode Standard Annex #9, version 13, also described in The Unicode Standard, Version 4.0 . 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

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

Bidi(AttributedCharacterIterator paragraph)
Create a Bidi object from the AttributedCharacterIterator of a paragraph text.

Bidi(char[] text, int textStart, byte[] embeddings, int embStart, int paragraphLength, int flags)
Create a Bidi object.

Bidi(String paragraph, int flags)
Create a Bidi object.

Method Summary

boolean	baseIsLeftToRight() Return whether the base level is from left to right.
Bidi	createLineBidi(int lineStart, int lineLimit) Create a new Bidi object containing the information of one line from this object.
int	getBaseLevel() Return the base level.
int	getLength() Return the length of the text in the Bidi object.
int	getLevelAt(int offset) Return the level of a specified character.
int	getRunCount() Return the number of runs in the bidirectional text.
int	getRunLevel(int run) Return the level of a specified run.
int	getRunLimit(int run) Return the limit offset of a specified run.
int	getRunStart(int run) Return the start offset of a specified run.
boolean	isLeftToRight() Return whether the text is from left to right, that is, both the base direction and the text direction is from left to right.
boolean	isMixed() Return whether the text direction is mixed.
boolean	isRightToLeft() Return whether 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) Reorder a range of objects according to their specified levels.
static boolean	requiresBidi(char[] text, int start, int limit) Return whether a range of characters of a text requires a Bidi object to display properly.
String	toString() Return the internal message of the Bidi object, used in debugging.

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)

Create a Bidi object from the AttributedCharacterIterator of a paragraph text. The RUN_DIRECTION attribute determines the base direction of the bidirectional text. If it's 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 - TODO Make these proper links again (problem with core vs. framework). see TextAttribute.BIDI_EMBEDDING see TextAttribute.NUMERIC_SHAPING see TextAttribute.RUN_DIRECTION

Bidi

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

Create a Bidi object.

Parameters:

text - the char array of the paragraph text.

textStart - the start offset of the text array to perform the algorithm.

embeddings - the embedding level array of the paragraph text, specifying the embedding level information 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.

embStart - the start offset of the embeddings array to perform the algorithm.

paragraphLength - the length of the text to perform the algorithm. It must be text.length >= textStart + paragraphLength, and embeddings.length >= embStart + paragraphLength.

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

Bidi

public Bidi(String paragraph,
            int flags)

Create a Bidi object.

Parameters:

paragraph - the String containing the paragraph 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.

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()

Return 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)

Create 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).

getBaseLevel

public int getBaseLevel()

Return the base level.

Returns:

the int value of the base level.

getLength

public int getLength()

Return the length of the text in the Bidi object.

Returns:

the int value of the length.

getLevelAt

public int getLevelAt(int offset)

Return the level of a specified character.

Parameters:

offset - the offset of the character.

Returns:

the int value of the level.

getRunCount

public int getRunCount()

Return the number of runs in the bidirectional text.

Returns:

the int value of runs, at least 1.

getRunLevel

public int getRunLevel(int run)

Return the level of a specified run.

Parameters:

run - the index of the run.

Returns:

the level of the run.

getRunLimit

public int getRunLimit(int run)

Return the limit offset of a specified run.

Parameters:

run - the index of the run.

Returns:

the limit offset of the run.

getRunStart

public int getRunStart(int run)

Return the start offset of a specified run.

Parameters:

run - the index of the run.

Returns:

the start offset of the run.

isLeftToRight

public boolean isLeftToRight()

Return whether the text is from left to right, that is, both the base direction and the text direction is from left to right.

Returns:

true if the text is from left to right.

isMixed

public boolean isMixed()

Return whether the text direction is mixed.

Returns:

true if the text direction is mixed.

isRightToLeft

public boolean isRightToLeft()

Return whether the text is from right to left, that is, both the base direction and the text direction is from right to left.

Returns:

true if the text is from right to left.

reorderVisually

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

Reorder 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.

requiresBidi

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

Return 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.

toString

public String toString()

Return the internal message of the Bidi object, used in debugging.

Overrides:

toString in class Object

Returns:

a string containing the internal message.