01: /*
02: * xtc - The eXTensible Compiler
03: * Copyright (C) 2004-2007 Robert Grimm
04: *
05: * This program is free software; you can redistribute it and/or
06: * modify it under the terms of the GNU General Public License
07: * version 2 as published by the Free Software Foundation.
08: *
09: * This program is distributed in the hope that it will be useful,
10: * but WITHOUT ANY WARRANTY; without even the implied warranty of
11: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12: * GNU General Public License for more details.
13: *
14: * You should have received a copy of the GNU General Public License
15: * along with this program; if not, write to the Free Software
16: * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
17: * USA.
18: */
19: package xtc.parser;
20:
21: /**
22: * Element to set the semantic value to <code>null</code>.
23: *
24: * @author Robert Grimm
25: * @version $Revision: 1.8 $
26: */
27: public class NullValue extends ValueElement {
28:
29: /** The canonical null value element. */
30: public static final NullValue VALUE = new NullValue();
31:
32: /** Hide the constructor. */
33: private NullValue() { /* Nothing to do. */
34: }
35:
36: public Tag tag() {
37: return Tag.NULL_VALUE;
38: }
39:
40: public int hashCode() {
41: return 5;
42: }
43:
44: public boolean equals(Object o) {
45: if (VALUE == o)
46: return true;
47: return (o instanceof NullValue);
48: }
49:
50: }
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