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Java > Open Source Codes > org > pdfbox > cos > COSNull


1 /**
2  * Copyright (c) 2003-2004, www.pdfbox.org
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright notice,
9  * this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright notice,
11  * this list of conditions and the following disclaimer in the documentation
12  * and/or other materials provided with the distribution.
13  * 3. Neither the name of pdfbox; nor the names of its
14  * contributors may be used to endorse or promote products derived from this
15  * software without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
18  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
20  * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
24  * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
26  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27  *
28  * http://www.pdfbox.org
29  *
30  */
31 package org.pdfbox.cos;
32
33
34
35 import java.io.IOException JavaDoc;
36 import java.io.OutputStream JavaDoc;
37
38 import org.pdfbox.exceptions.COSVisitorException;
39
40 /**
41  * This class represents a null PDF object.
42  *
43  * @author <a HREF="mailto:ben@benlitchfield.com">Ben Litchfield</a>
44  * @version $Revision: 1.13 $
45  */
46 public class COSNull extends COSBase
47 {
48     /**
49      * The null token.
50      */
51     public static final byte[] NULL_BYTES = new byte[] {110, 117, 108, 108}; //"null".getBytes( "ISO-8859-1" );
52
53     /**
54      * The one null object in the system.
55      */
56     public static final COSNull NULL = new COSNull();
57
58     /**
59      * Constructor.
60      */
61     private COSNull()
62     {
63         //limit creation to one instance.
64 }
65
66     /**
67      * visitor pattern double dispatch method.
68      *
69      * @param visitor The object to notify when visiting this object.
70      * @return any object, depending on the visitor implementation, or null
71      * @throws COSVisitorException If an error occurs while visiting this object.
72      */
73     public Object JavaDoc accept( ICOSVisitor visitor ) throws COSVisitorException
74     {
75         return visitor.visitFromNull( this );
76     }
77     
78     /**
79      * This will output this string as a PDF object.
80      *
81      * @param output The stream to write to.
82      * @throws IOException If there is an error writing to the stream.
83      */
84     public void writePDF( OutputStream JavaDoc output ) throws IOException JavaDoc
85     {
86         output.write(NULL_BYTES);
87     }
88 }
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