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 ( ); } |