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//
// ========================================================================
// Copyright (c) 1995-2016 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package org.eclipse.jetty.util;
/**
* <p>A callback abstraction that handles completed/failed events of asynchronous operations.</p>
*
* <p>Semantically this is equivalent to an optimise Promise<Void>, but callback is a more meaningful
* name than EmptyPromise</p>
*/
public interface Callback
{
/**
* Instance of Adapter that can be used when the callback methods need an empty
* implementation without incurring in the cost of allocating a new Adapter object.
*/
static Callback NOOP = new Callback(){};
/**
* <p>Callback invoked when the operation completes.</p>
*
* @see #failed(Throwable)
*/
default void succeeded()
{}
/**
* <p>Callback invoked when the operation fails.</p>
* @param x the reason for the operation failure
*/
default void failed(Throwable x)
{}
/**
* @return True if the callback is known to never block the caller
*/
default boolean isNonBlocking()
{
return false;
}
/**
* Callback interface that declares itself as non-blocking
*/
interface NonBlocking extends Callback
{
@Override
public default boolean isNonBlocking()
{
return true;
}
}
/**
* <p>Empty implementation of {@link Callback}</p>
*/
@Deprecated
static class Adapter implements Callback
{}
}
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