1 /* Licensed to the Apache Software Foundation (ASF) under one or more
2  * contributor license agreements.  See the NOTICE file distributed with
3  * this work for additional information regarding copyright ownership.
4  * The ASF licenses this file to You under the Apache License, Version 2.0
5  * (the "License"); you may not use this file except in compliance with
6  * the License.  You may obtain a copy of the License at
7  *
8  *     http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package java.nio.channels;
18 
19 import java.io.Closeable;
20 import java.io.IOException;
21 
22 /**
23  * A channel is a conduit to I/O services covering such items as files, sockets,
24  * hardware devices, I/O ports or some software component.
25  * <p>
26  * Channels are open upon creation, and can be closed explicitly. Once a channel
27  * is closed it cannot be re-opened, and any attempts to perform I/O operations
28  * on the closed channel result in a <code>ClosedChannelException</code>.
29  * <p>
30  * Particular implementations or sub-interfaces of {@code Channel} dictate
31  * whether they are thread-safe or not.
32  */
33 public interface Channel extends Closeable {
34 
35     /**
36      * Returns true if this channel is open.
37      */
isOpen()38     public boolean isOpen();
39 
40     /**
41      * Closes an open channel. If the channel is already closed then this method
42      * has no effect. If there is a problem with closing the channel then the
43      * method throws an IOException and the exception contains reasons for the
44      * failure.
45      * <p>
46      * If an attempt is made to perform an operation on a closed channel then a
47      * {@link ClosedChannelException} will be thrown on that attempt.
48      * <p>
49      * If multiple threads attempt to simultaneously close a channel, then only
50      * one thread will run the closure code, and others will be blocked until
51      * the first returns.
52      *
53      * @throws IOException
54      *             if a problem occurs closing the channel.
55      */
close()56     public void close() throws IOException;
57 }
58