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Java > Open Source Codes > com > caucho > relaxng > program > EmptyItem


1 /*
2  * Copyright (c) 1998-2006 Caucho Technology -- all rights reserved
3  *
4  * This file is part of Resin(R) Open Source
5  *
6  * Each copy or derived work must preserve the copyright notice and this
7  * notice unmodified.
8  *
9  * Resin Open Source is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License as published by
11  * the Free Software Foundation; either version 2 of the License, or
12  * (at your option) any later version.
13  *
14  * Resin Open Source is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
17  * of NON-INFRINGEMENT. See the GNU General Public License for more
18  * details.
19  *
20  * You should have received a copy of the GNU General Public License
21  * along with Resin Open Source; if not, write to the
22  * Free SoftwareFoundation, Inc.
23  * 59 Temple Place, Suite 330
24  * Boston, MA 02111-1307 USA
25  *
26  * @author Scott Ferguson
27  */
28
29 package com.caucho.relaxng.program;
30
31 import com.caucho.util.L10N;
32 import com.caucho.xml.QName;
33
34 import java.util.HashSet JavaDoc;
35
36 /**
37  * Generates programs from patterns.
38  */
39 public class EmptyItem extends Item {
40   protected final static L10N L = new L10N(EmptyItem.class);
41
42   private static final EmptyItem EMPTY = new EmptyItem();
43
44   /**
45    * Creates the empty item.
46    */
47   public static EmptyItem create()
48   {
49     return EMPTY;
50   }
51
52   /**
53    * Adds to the first set, the set of element names possible.
54    */
55   public void firstSet(HashSet JavaDoc<QName> set)
56   {
57   }
58   
59   /**
60    * The empty item can produce empty.
61    */
62   public boolean allowEmpty()
63   {
64     return true;
65   }
66   
67   /**
68    * Sets an attribute.
69    *
70    * @param name the name of the attribute
71    * @param value the value of the attribute
72    *
73    * @return the program for handling the element
74    */
75   public Item setAttribute(QName name, String JavaDoc value)
76   {
77     return this;
78   }
79
80   /**
81    * Returns the pretty printed syntax.
82    */
83   public String JavaDoc toSyntaxDescription(int depth)
84   {
85     return "empty";
86   }
87
88   /**
89    * True for simple syntax.
90    */
91   public boolean isSimpleSyntax()
92   {
93     return true;
94   }
95
96   /**
97    * Returns the hash code for the empty item.
98    */
99   public int hashCode()
100   {
101     return 37;
102   }
103
104   /**
105    * Returns true if the object is an empty item.
106    */
107   public boolean equals(Object JavaDoc o)
108   {
109     return o instanceof EmptyItem;
110   }
111
112   public String JavaDoc toString()
113   {
114     return "EmptyItem[]";
115   }
116 }
117
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