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Java > Open Source Codes > org > antlr > works > navigation > GoToHistory


1 /*
2
3 [The "BSD licence"]
4 Copyright (c) 2005 Jean Bovet
5 All rights reserved.
6
7 Redistribution and use in source and binary forms, with or without
8 modification, are permitted provided that the following conditions
9 are met:
10
11 1. Redistributions of source code must retain the above copyright
12 notice, this list of conditions and the following disclaimer.
13 2. Redistributions in binary form must reproduce the above copyright
14 notice, this list of conditions and the following disclaimer in the
15 documentation and/or other materials provided with the distribution.
16 3. The name of the author may not be used to endorse or promote products
17 derived from this software without specific prior written permission.
18
19 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29
30 */

31
32
33 package org.antlr.works.navigation;
34
35 import java.util.ArrayList JavaDoc;
36 import java.util.List JavaDoc;
37
38 public class GoToHistory {
39
40     protected List JavaDoc<Integer JavaDoc> history = new ArrayList JavaDoc<Integer JavaDoc>();
41     protected int currentIndex = 0;
42
43     public GoToHistory() {
44
45     }
46
47     public void addPosition(int pos) {
48         // Erase the remaining portion of the history
49
// when adding a new position (forward
50
// doesn't make sense anymore)
51
int index = history.size()-1;
52         while(index >= currentIndex) {
53             history.remove(index);
54             index--;
55         }
56         history.add(pos);
57         currentIndex = history.size();
58     }
59
60     public boolean canGoBack() {
61         return !history.isEmpty() && currentIndex > 0;
62     }
63
64     public boolean canGoForward() {
65         return !history.isEmpty() && currentIndex < history.size()-1;
66     }
67
68     public int getBackPosition(int currentPosition) {
69         if(currentIndex == history.size()) {
70             // Add the current position if the currentIndex
71
// is at the end of the history (so Forward is able
72
// to come back)
73
history.add(currentPosition);
74         }
75
76         currentIndex--;
77         if(currentIndex < 0)
78             currentIndex = 0;
79         return history.get(currentIndex);
80     }
81
82     public int getForwardPosition() {
83         currentIndex++;
84         if(currentIndex >= history.size())
85             currentIndex = history.size()-1;
86         return history.get(currentIndex);
87     }
88 }
89
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