The Bidi class implements the
"
Unicode Version 3.0 Bidirectional
Algorithm" for working with Arabic and Hebrew text
in which letters run right-to-left and numbers run left-to-right. It
is named after the first four letters of
"bidirectional." A full description
of the bidirectional text handling and the bidirectional algorithim
is beyond the scope of this book, but the simplest use case for this
class is outlined here. Create a Bidi object by
passing an AttributedCharacterIterator or a
String and one of the DIRECTION
constants (to indicate the base direction of the text) to the
Bidi( ) constructor. Or use
createLineBidi( ) to return a substring of an
existing Bidi object (this is usually done when
formatting a paragraph of text to fit on individual lines).Once you have a Bidi object, use
isLeftToRight( ) and isRightToLeft(
) to determine whether all the text has the same direction.
If both of these methods return false (which is
the same as isMixed( ) returning
TRue) then you cannot treat the text as a single
run of uni-directional text. In this case, you must break it into two
or more runs of unidirectional text. getrunCount(
) returns the number of distinct runs of text. For each
such numbered run, getrunStart( ) returns the
index of the first character of the run, and geTRunLimit(
) returns the index of the first character past the end of
the run. getrunLevel( ) returns the
level of the text, which is an integer that
represents the direction and nesting level of the text. Even levels
represent left-to-right text, and odd levels represent right-to-left
text. The level divided by two is the nesting level of the text. For
example, left-to-right text embedded within right-to-left text has a
level of 2.public final class Bidi {
// Public Constructors
public Bidi (AttributedCharacterIterator paragraph );
public Bidi (String paragraph , int flags );
public Bidi (char[ ] text , int textStart , byte[ ] embeddings ,
int embStart , int paragraphLength , int flags );
// Public Constants
public static final int DIRECTION_DEFAULT_LEFT_TO_RIGHT ; =-2
public static final int DIRECTION_DEFAULT_RIGHT_TO_LEFT ; =-1
public static final int DIRECTION_LEFT_TO_RIGHT ; =0
public static final int DIRECTION_RIGHT_TO_LEFT ; =1
// Public Class Methods
public static void reorderVisually (byte[ ] levels , int levelStart ,
Object[ ] objects , int objectStart , int count );
public static boolean requiresBidi (char[ ] text , int start , int limit );
// Public Instance Methods
public boolean baseIsLeftToRight ( );
public Bidi createLineBidi (int lineStart , int lineLimit );
public int getBaseLevel ( );
public int getLength ( );
public int getLevelAt (int offset );
public int getRunCount ( );
public int getRunLevel (int run );
public int getRunLimit (int run );
public int getRunStart (int run );
public boolean isLeftToRight ( );
public boolean isMixed ( );
public boolean isRightToLeft ( );
// Public Methods Overriding Object
public String toString ( );
}
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