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Java > Open Source Codes > edu > umd > cs > findbugs > ba > type > BottomType


1 /*
2  * Bytecode Analysis Framework
3  * Copyright (C) 2003,2004 University of Maryland
4  *
5  * This library is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU Lesser General Public
7  * License as published by the Free Software Foundation; either
8  * version 2.1 of the License, or (at your option) any later version.
9  *
10  * This library is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13  * Lesser General Public License for more details.
14  *
15  * You should have received a copy of the GNU Lesser General Public
16  * License along with this library; if not, write to the Free Software
17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18  */
19
20 package edu.umd.cs.findbugs.ba.type;
21
22 import org.apache.bcel.generic.Type;
23
24 /**
25  * Special "bottom" type.
26  * It is the zero element for the type merge operation.
27  *
28  * @author David Hovemeyer
29  * @see TypeAnalysis
30  * @see TypeFrame
31  * @see TypeMerger
32  */
33 public class BottomType extends Type implements ExtendedTypes {
34     /**
35      *
36      */
37     private static final long serialVersionUID = 1L;
38     private static final BottomType theInstance = new BottomType();
39
40     private BottomType() {
41         super(T_BOTTOM, "<bottom>");
42     }
43
44     @Override JavaDoc
45          public int hashCode() {
46         return System.identityHashCode(this);
47     }
48
49     @Override JavaDoc
50          public boolean equals(Object JavaDoc o) {
51         return o == this;
52     }
53
54     /**
55      * Get the single instance of the bottom type.
56      */
57     public static Type instance() {
58         return theInstance;
59     }
60 }
61
62 // vim:ts=4
63
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