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Java > Open Source Codes > bluej > editor > moe > TextUtilities


1 package bluej.editor.moe;
2
3 /*
4  * TextUtilities.java - Utility functions used by the text area classes
5  * Copyright (C) 1999 Slava Pestov
6  *
7  * You may use and modify this package for any purpose. Redistribution is
8  * permitted, in both source and binary form, provided that this notice
9  * remains intact in all source distributions of this package.
10  */
11
12 import javax.swing.text.*;
13
14 /**
15  * Class with several utility functions used by the text area component.
16  * @author Slava Pestov
17  * @version $Id: TextUtilities.java,v 1.1 2002/07/16 00:10:11 bquig Exp $
18  */
19 public class TextUtilities
20 {
21     /**
22      * Returns the offset of the bracket matching the one at the
23      * specified offset of the document, or -1 if the bracket is
24      * unmatched (or if the character is not a bracket).
25      * @param doc The document
26      * @param offset The offset
27      * @exception BadLocationException If an out-of-bounds access
28      * was attempted on the document text
29      */
30     public static int findMatchingBracket(Document doc, int offset)
31         throws BadLocationException
32     {
33         if(doc.getLength() == 0)
34             return -1;
35         char c = doc.getText(offset, 1).charAt(0);
36         char cprime; // c` - corresponding character
37 boolean direction; // true = back, false = forward
38
39         switch(c)
40         {
41         case '(': cprime = ')'; direction = false; break;
42         case ')': cprime = '('; direction = true; break;
43         case '[': cprime = ']'; direction = false; break;
44         case ']': cprime = '['; direction = true; break;
45         case '{': cprime = '}'; direction = false; break;
46         case '}': cprime = '{'; direction = true; break;
47         default: return -1;
48         }
49
50         int count;
51
52         // How to merge these two cases is left as an exercise
53 // for the reader.
54
55         // Go back or forward
56 if(direction)
57         {
58             // Count is 1 initially because we have already
59 // `found' one closing bracket
60 count = 1;
61
62             // Get text[0,offset-1];
63 String JavaDoc text = doc.getText(0,offset);
64
65             // Scan backwards
66 for(int i = offset - 1; i >= 0; i--)
67             {
68                 // If text[i] == c, we have found another
69 // closing bracket, therefore we will need
70 // two opening brackets to complete the
71 // match.
72 char x = text.charAt(i);
73                 if(x == c)
74                     count++;
75
76                 // If text[i] == cprime, we have found a
77 // opening bracket, so we return i if
78 // --count == 0
79 else if(x == cprime)
80                 {
81                     if(--count == 0)
82                         return i;
83                 }
84             }
85         }
86         else
87         {
88             // Count is 1 initially because we have already
89 // `found' one opening bracket
90 count = 1;
91
92             // So we don't have to + 1 in every loop
93 offset++;
94
95             // Number of characters to check
96 int len = doc.getLength() - offset;
97
98             // Get text[offset+1,len];
99 String JavaDoc text = doc.getText(offset,len);
100
101             // Scan forwards
102 for(int i = 0; i < len; i++)
103             {
104                 // If text[i] == c, we have found another
105 // opening bracket, therefore we will need
106 // two closing brackets to complete the
107 // match.
108 char x = text.charAt(i);
109
110                 if(x == c)
111                     count++;
112
113                 // If text[i] == cprime, we have found an
114 // closing bracket, so we return i if
115 // --count == 0
116 else if(x == cprime)
117                 {
118                     if(--count == 0)
119                         return i + offset;
120                 }
121             }
122         }
123
124         // Nothing found
125 return -1;
126     }
127
128     /**
129      * Locates the start of the word at the specified position.
130      * @param line The text
131      * @param pos The position
132      */
133     public static int findWordStart(String JavaDoc line, int pos, String JavaDoc noWordSep)
134     {
135         char ch = line.charAt(pos - 1);
136
137         if(noWordSep == null)
138             noWordSep = "";
139         boolean selectNoLetter = (!Character.isLetterOrDigit(ch)
140             && noWordSep.indexOf(ch) == -1);
141
142         int wordStart = 0;
143         for(int i = pos - 1; i >= 0; i--)
144         {
145             ch = line.charAt(i);
146             if(selectNoLetter ^ (!Character.isLetterOrDigit(ch) &&
147                 noWordSep.indexOf(ch) == -1))
148             {
149                 wordStart = i + 1;
150                 break;
151             }
152         }
153
154         return wordStart;
155     }
156
157     /**
158      * Locates the end of the word at the specified position.
159      * @param line The text
160      * @param pos The position
161      */
162     public static int findWordEnd(String JavaDoc line, int pos, String JavaDoc noWordSep)
163     {
164         char ch = line.charAt(pos);
165
166         if(noWordSep == null)
167             noWordSep = "";
168         boolean selectNoLetter = (!Character.isLetterOrDigit(ch)
169             && noWordSep.indexOf(ch) == -1);
170
171         int wordEnd = line.length();
172         for(int i = pos; i < line.length(); i++)
173         {
174             ch = line.charAt(i);
175             if(selectNoLetter ^ (!Character.isLetterOrDigit(ch) &&
176                 noWordSep.indexOf(ch) == -1))
177             {
178                 wordEnd = i;
179                 break;
180             }
181         }
182         return wordEnd;
183     }
184 }
185
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