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      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      */
     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      */
     56     public void close() throws IOException;
     57 }
     58