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package java.nio.channels;

A handler for consuming the result of an asynchronous I/O operation.
 The asynchronous channels defined in this package allow a completion handler to be specified to consume the result of an asynchronous operation. The completed method is invoked when the I/O operation completes successfully. The failed method is invoked if the I/O operations fails. The implementations of these methods should complete in a timely manner so as to avoid keeping the invoking thread from dispatching to other completion handlers. 
Type parameters:
<V> –     The result type of the I/O operation
<A> –     The type of the object attached to the I/O operation
Since:
1.7/**
 * A handler for consuming the result of an asynchronous I/O operation.
 *
 * <p> The asynchronous channels defined in this package allow a completion
 * handler to be specified to consume the result of an asynchronous operation.
 * The {@link #completed completed} method is invoked when the I/O operation
 * completes successfully. The {@link #failed failed} method is invoked if the
 * I/O operations fails. The implementations of these methods should complete
 * in a timely manner so as to avoid keeping the invoking thread from dispatching
 * to other completion handlers.
 *
 * @param   <V>     The result type of the I/O operation
 * @param   <A>     The type of the object attached to the I/O operation
 *
 * @since 1.7
 */

public interface CompletionHandler<V,A> {

    
Invoked when an operation has completed.
Params:
result – 
         The result of the I/O operation.
attachment – 
         The object attached to the I/O operation when it was initiated./**
     * Invoked when an operation has completed.
     *
     * @param   result
     *          The result of the I/O operation.
     * @param   attachment
     *          The object attached to the I/O operation when it was initiated.
     */
    void completed(V result, A attachment);

    
Invoked when an operation fails.
Params:
exc – 
         The exception to indicate why the I/O operation failed
attachment – 
         The object attached to the I/O operation when it was initiated./**
     * Invoked when an operation fails.
     *
     * @param   exc
     *          The exception to indicate why the I/O operation failed
     * @param   attachment
     *          The object attached to the I/O operation when it was initiated.
     */
    void failed(Throwable exc, A attachment);
}