01: /**
02: * Copyright (c) 2003-2004, www.pdfbox.org
03: * All rights reserved.
04: *
05: * Redistribution and use in source and binary forms, with or without
06: * modification, are permitted provided that the following conditions are met:
07: *
08: * 1. Redistributions of source code must retain the above copyright notice,
09: * 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: */package org.pdfbox.cos;
31:
32: import java.io.IOException;
33: import java.io.OutputStream;
34:
35: import org.pdfbox.exceptions.COSVisitorException;
36:
37: /**
38: * This class represents a null PDF object.
39: *
40: * @author <a href="mailto:ben@benlitchfield.com">Ben Litchfield</a>
41: * @version $Revision: 1.13 $
42: */
43: public class COSNull extends COSBase {
44: /**
45: * The null token.
46: */
47: public static final byte[] NULL_BYTES = new byte[] { 110, 117, 108,
48: 108 }; //"null".getBytes( "ISO-8859-1" );
49:
50: /**
51: * The one null object in the system.
52: */
53: public static final COSNull NULL = new COSNull();
54:
55: /**
56: * Constructor.
57: */
58: private COSNull() {
59: //limit creation to one instance.
60: }
61:
62: /**
63: * visitor pattern double dispatch method.
64: *
65: * @param visitor The object to notify when visiting this object.
66: * @return any object, depending on the visitor implementation, or null
67: * @throws COSVisitorException If an error occurs while visiting this object.
68: */
69: public Object accept(ICOSVisitor visitor)
70: throws COSVisitorException {
71: return visitor.visitFromNull(this );
72: }
73:
74: /**
75: * This will output this string as a PDF object.
76: *
77: * @param output The stream to write to.
78: * @throws IOException If there is an error writing to the stream.
79: */
80: public void writePDF(OutputStream output) throws IOException {
81: output.write(NULL_BYTES);
82: }
83: }
|