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TopicData.java
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TopicData.java
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/*
* Copyright (c) 2019 Contributors to the Eclipse Foundation
*
* See the NOTICE file(s) distributed with this work for additional
* information regarding copyright ownership.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0
*
* SPDX-License-Identifier: EPL-2.0
*/
package org.eclipse.ditto.internal.utils.pubsub.ddata;
import java.util.HashSet;
import java.util.Objects;
import java.util.Set;
import javax.annotation.concurrent.NotThreadSafe;
import org.apache.pekko.actor.ActorRef;
/**
* Set of subscribers of a topic together with its hashes.
*/
@NotThreadSafe
public final class TopicData {
private final Set<ActorRef> subscribers;
private TopicData(final Set<ActorRef> subscribers) {
this.subscribers = subscribers;
}
/**
* Create topic data upon arrival of the first subscriber.
*
* @param subscriber the first subscriber.
* @return the topic data.
*/
public static TopicData firstSubscriber(final ActorRef subscriber) {
final Set<ActorRef> subscribers = new HashSet<>();
subscribers.add(subscriber);
return new TopicData(subscribers);
}
/**
* Add a subscriber to the topic.
*
* @param newSubscriber the new subscriber.
* @return whether this object changed.
*/
public boolean addSubscriber(final ActorRef newSubscriber) {
return subscribers.add(newSubscriber);
}
/**
* Remove a subscriber from the topic.
*
* @param subscriber who is being removed.
* @return whether this object changed.
*/
public boolean removeSubscriber(final ActorRef subscriber) {
return subscribers.remove(subscriber);
}
/**
* @return whether there are no subscribers.
*/
public boolean isEmpty() {
return subscribers.isEmpty();
}
/**
* @return an unmodifiable copy of the set of subscribers.
*/
public Set<ActorRef> exportSubscribers() {
return Set.copyOf(subscribers);
}
@Override
public boolean equals(final Object other) {
if (other instanceof TopicData) {
final TopicData that = (TopicData) other;
return subscribers.equals(that.subscribers);
} else {
return false;
}
}
@Override
public int hashCode() {
return Objects.hash(subscribers);
}
}