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1   /*
2    * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24   */
25  
26  package java.nio.channels;
27  
28  import java.io.IOException;
29  import java.io.Closeable;
30  
31  
32  /**
33   * A nexus for I/O operations.
34   *
35   * <p> A channel represents an open connection to an entity such as a hardware
36   * device, a file, a network socket, or a program component that is capable of
37   * performing one or more distinct I/O operations, for example reading or
38   * writing.
39   *
40   * <p> A channel is either open or closed.  A channel is open upon creation,
41   * and once closed it remains closed.  Once a channel is closed, any attempt to
42   * invoke an I/O operation upon it will cause a {@link ClosedChannelException}
43   * to be thrown.  Whether or not a channel is open may be tested by invoking
44   * its {@link #isOpen isOpen} method.
45   *
46   * <p> Channels are, in general, intended to be safe for multithreaded access
47   * as described in the specifications of the interfaces and classes that extend
48   * and implement this interface.
49   *
50   *
51   * @author Mark Reinhold
52   * @author JSR-51 Expert Group
53   * @since 1.4
54   */
55  
56  public interface Channel extends Closeable {
57  
58      /**
59       * Tells whether or not this channel is open.
60       *
61       * @return <tt>true</tt> if, and only if, this channel is open
62       */
63      public boolean isOpen();
64  
65      /**
66       * Closes this channel.
67       *
68       * <p> After a channel is closed, any further attempt to invoke I/O
69       * operations upon it will cause a {@link ClosedChannelException} to be
70       * thrown.
71       *
72       * <p> If this channel is already closed then invoking this method has no
73       * effect.
74       *
75       * <p> This method may be invoked at any time.  If some other thread has
76       * already invoked it, however, then another invocation will block until
77       * the first invocation is complete, after which it will return without
78       * effect. </p>
79       *
80       * @throws  IOException  If an I/O error occurs
81       */
82      public void close() throws IOException;
83  
84  }