/*
* Copyright (c) 2014, grossmann
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the jo-widgets.org nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL jo-widgets.org BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*/
package org.jowidgets.util.collection;
/**
* A set designed to hold observers when implementing the observer pattern
*
* For this use case, the set has the following contract
*
* 1. Observers exists only once (its a set), adding them a second time will not modify the set
*
* This will be done to avoid that listeners will be fired more than once in the case they was added accidently more than once.
* This also ensures, that after invoking the remove() method the listener no longer remains in the set because it was added more
* than once before accidently. This protects from heavy to find bugs where listeners was not removed correctly.
*
* 2. Iteration over the set is done in the same order the elements was added
*
* It's reasonable to iterate always in the same order to avoid indeterministic behavior, e.g. to reproduce bugs.
*
* 3. Iteration is always done with a defensive copy, so changing the set while iterating over it is explicitly allowed,
* but the iterator itself is unmodifiable. So changing the set while iterating over it must be done with add() and remove()
*
* The are many cases where it is very practical the remove a listener while it will be invoked, e.g. on dispose or for binding
* issues
*
*
* Implementations have not to be threadsafe. Implementors can assume that all modifications will be done
* in the same thread and have not have to check the thread explicitly.
*
* @param <OBSERVER_TYPE> The type of the observer hold by this set
*/
public interface IObserverSet<OBSERVER_TYPE> extends Iterable<OBSERVER_TYPE> {
/**
* Adds an observer to the set. If the observer was added already, the set remains unchanged
*
* @param observer The observer to add, not null
*
* @throws IllegalArgumentException if the observer is null
*/
void add(OBSERVER_TYPE observer);
/**
* Removes an observer from the set. If the observer is not a element of the set, the set remains unchanged
*
* @param observer The observer to remove, not null
*
* @return true if the set container the given element (and so it was removed)
*
* @throws IllegalArgumentException if the given observer is null
*/
boolean remove(OBSERVER_TYPE observer);
/**
* Removes all elements from the set an releases the used memory
*/
void clear();
}