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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      */
isOpen()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      */
close()82     public void close() throws IOException;
83 
84 }
85