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Java > Open Source Codes > com > hp > hpl > jena > shared > wg > LazyInputStream


1 /*
2  * (c) Copyright 2000, 2001, 2002, 2003, 2004, 2005 Hewlett-Packard Development Company, LP
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
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  * notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  * notice, this list of conditions and the following disclaimer in the
12  * documentation and/or other materials provided with the distribution.
13  * 3. The name of the author may not be used to endorse or promote products
14  * derived from this software without specific prior written permission.
15  
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26  *
27  *
28  * LazyZipEntryInputStream.java
29  *
30  * Created on November 28, 2001, 11:38 AM
31  */
32
33 package com.hp.hpl.jena.shared.wg;
34
35
36 import java.io.*;
37
38 /**
39  *In test cases we cannot open all the input files
40  * while creating the test suite, but must defer the
41  * opening until the test is actually run.
42  * @author jjc
43  */
44 abstract class LazyInputStream extends InputStream {
45
46     private InputStream underlying;
47     abstract InputStream open() throws IOException;
48     
49     boolean connect() throws IOException {
50         if ( underlying != null )
51           return true;
52         else {
53             underlying = open();
54         }
55         return underlying != null;
56             
57     }
58     
59     
60     public int read() throws IOException {
61         if (underlying == null)
62             underlying = open();
63         return underlying.read();
64     }
65     
66     public void close() throws IOException {
67         if (underlying != null) {
68             underlying.close();
69             underlying = null;
70         }
71     }
72     
73     
74
75 }
76
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