Returns the offset of the bracket matching the one at the specified offset of the document : SwingUtilities « Swing « Java Tutorial





/*
 * TextUtilities.java - Utility functions used by the text area classes
 * Copyright (C) 1999 Slava Pestov
 *
 * You may use and modify this package for any purpose. Redistribution is
 * permitted, in both source and binary form, provided that this notice
 * remains intact in all source distributions of this package.
 */



import javax.swing.text.BadLocationException;
import javax.swing.text.Document;

/**
 * Class with several utility functions used by the text area component.
 * 
 * @author Slava Pestov
 * @version $Id$
 */
public class TextUtilities
{
  /**
   * Returns the offset of the bracket matching the one at the specified offset
   * of the document, or -1 if the bracket is unmatched (or if the character is
   * not a bracket).
   * 
   * @param doc
   *           The document
   * @param offset
   *           The offset
   * @exception BadLocationException
   *               If an out-of-bounds access was attempted on the document
   *               text
   */
  public static int findMatchingBracket( Document doc, int offset ) throws BadLocationException
  {
    if( doc.getLength() == 0 )
      return -1;
    char c = doc.getText( offset, 1 ).charAt( 0 );
    char cprime; // c` - corresponding character
    boolean direction; // true = back, false = forward

    switch( c )
    {
    case '(' :
      cprime = ')';
      direction = false;
      break;
    case ')' :
      cprime = '(';
      direction = true;
      break;
    case '[' :
      cprime = ']';
      direction = false;
      break;
    case ']' :
      cprime = '[';
      direction = true;
      break;
    case '{' :
      cprime = '}';
      direction = false;
      break;
    case '}' :
      cprime = '{';
      direction = true;
      break;
    default :
      return -1;
    }

    int count;

    // How to merge these two cases is left as an exercise
    // for the reader.

    // Go back or forward
    if( direction )
    {
      // Count is 1 initially because we have already
      // `found' one closing bracket
      count = 1;

      // Get text[0,offset-1];
      String text = doc.getText( 0, offset );

      // Scan backwards
      for( int i = offset - 1; i >= 0; i-- )
      {
        // If text[i] == c, we have found another
        // closing bracket, therefore we will need
        // two opening brackets to complete the
        // match.
        char x = text.charAt( i );
        if( x == c )
          count++ ;

        // If text[i] == cprime, we have found a
        // opening bracket, so we return i if
        // --count == 0
        else if( x == cprime )
        {
          if( --count == 0 )
            return i;
        }
      }
    }
    else
    {
      // Count is 1 initially because we have already
      // `found' one opening bracket
      count = 1;

      // So we don't have to + 1 in every loop
      offset++ ;

      // Number of characters to check
      int len = doc.getLength() - offset;

      // Get text[offset+1,len];
      String text = doc.getText( offset, len );

      // Scan forwards
      for( int i = 0; i < len; i++ )
      {
        // If text[i] == c, we have found another
        // opening bracket, therefore we will need
        // two closing brackets to complete the
        // match.
        char x = text.charAt( i );

        if( x == c )
          count++ ;

        // If text[i] == cprime, we have found an
        // closing bracket, so we return i if
        // --count == 0
        else if( x == cprime )
        {
          if( --count == 0 )
            return i + offset;
        }
      }
    }

    // Nothing found
    return -1;
  }

}










14.127.SwingUtilities
14.127.1.Getting the JFrame of a Component
14.127.2.Convert a coordinate relative to a component's bounds to screen coordinates
14.127.3.Convert a coordinate on a screen to a coordinate relative to a component's bounds
14.127.4.Handle long-running tasks in a Swing application
14.127.5.Get the JFrame by getting the root of a component
14.127.6.Positions the specified frame at a relative position in the screen, where 50% is considered to be the center of the screen.
14.127.7.Positions the specified frame in the middle of the screen.
14.127.8.Positions the specified frame at a random location on the screen while ensuring that the
14.127.9.Get Window from a component
14.127.10.Center that window on the given desktop.
14.127.11.Get All Components in a container
14.127.12.Get Point For Centering
14.127.13.Is Within Parent
14.127.14.Show the given frame as modal to the specified owner
14.127.15.Change the sizes of all the passed buttons to be the size of the largest one.
14.127.16.Get Screen Bounds For
14.127.17.Returns the offset of the bracket matching the one at the specified offset of the document