XNull.java revision 628:2bfaf29cc90b 
1/*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5/*
6 * Copyright 1999-2004 The Apache Software Foundation.
7 *
8 * Licensed under the Apache License, Version 2.0 (the "License");
9 * you may not use this file except in compliance with the License.
10 * You may obtain a copy of the License at
11 *
12 *     http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS,
16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 * See the License for the specific language governing permissions and
18 * limitations under the License.
19 */
20/*
21 * $Id: XNull.java,v 1.2.4.1 2005/09/14 20:34:46 jeffsuttor Exp $
22 */
23package com.sun.org.apache.xpath.internal.objects;
24
25import com.sun.org.apache.xml.internal.dtm.DTM;
26import com.sun.org.apache.xpath.internal.XPathContext;
27
28/**
29 * This class represents an XPath null object, and is capable of
30 * converting the null to other types, such as a string.
31 * @xsl.usage general
32 */
33public class XNull extends XNodeSet
34{
35    static final long serialVersionUID = -6841683711458983005L;
36
37  /**
38   * Create an XObject.
39   */
40  public XNull()
41  {
42    super();
43  }
44
45  /**
46   * Tell what kind of class this is.
47   *
48   * @return type CLASS_NULL
49   */
50  public int getType()
51  {
52    return CLASS_NULL;
53  }
54
55  /**
56   * Given a request type, return the equivalent string.
57   * For diagnostic purposes.
58   *
59   * @return type string "#CLASS_NULL"
60   */
61  public String getTypeString()
62  {
63    return "#CLASS_NULL";
64  }
65
66  /**
67   * Cast result object to a number.
68   *
69   * @return 0.0
70   */
71
72  public double num()
73  {
74    return 0.0;
75  }
76
77  /**
78   * Cast result object to a boolean.
79   *
80   * @return false
81   */
82  public boolean bool()
83  {
84    return false;
85  }
86
87  /**
88   * Cast result object to a string.
89   *
90   * @return empty string ""
91   */
92  public String str()
93  {
94    return "";
95  }
96
97  /**
98   * Cast result object to a result tree fragment.
99   *
100   * @param support XPath context to use for the conversion
101   *
102   * @return The object as a result tree fragment.
103   */
104  public int rtf(XPathContext support)
105  {
106    // DTM frag = support.createDocumentFragment();
107    // %REVIEW%
108    return DTM.NULL;
109  }
110
111//  /**
112//   * Cast result object to a nodelist.
113//   *
114//   * @return null
115//   */
116//  public DTMIterator iter()
117//  {
118//    return null;
119//  }
120
121  /**
122   * Tell if two objects are functionally equal.
123   *
124   * @param obj2 Object to compare this to
125   *
126   * @return True if the given object is of type CLASS_NULL
127   */
128  public boolean equals(XObject obj2)
129  {
130    return obj2.getType() == CLASS_NULL;
131  }
132}
133