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/* Copyright (C) 2013-2019 TU Dortmund
* This file is part of AutomataLib, http://www.automatalib.net/.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package net.automatalib.commons.smartcollections;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.ParametersAreNonnullByDefault;
/**
* An extended collection interface.
*
* This interface overcomes various shortcomings of the {@link Collection} interface from the Java Collections
* Framework, and also introduces other features not present in other libraries (such as the Apache Commons Collections
* Library).
*
* Efficiently operating on collections data structures is often hampered by the insufficient interface provided by the
* standard Java collections.
*
* For example, linked lists allow constant time removal if the element to be removed is known. However, using {@link
* List#remove(int)} requires linear time in the provided parameter (and thus, in the worst case, linear time in the
* size of the list). Removal in constant time is possible when iterating manually using the {@link Iterator#remove()}
* method, but this is not only inconvenient, but also does not work if one wants to remove the elements later, because
* {@link Iterator}s can't be cloned, and additionally are invalidated by other modifications of the underlying
* collection during their existence.
*
* This collection interface introduces a reference concept: References (represented by the marker interface
* {@link ElementReference}) to the elements allow efficient (in terms of what the data structure itself supports)
* operations on the elements, if the reference to the respective element is known. References can be acquired right at
* the point when an element is added to the collection (using {@link #referencedAdd(Object)}), by explicitly searching
* for an element (using {@link #find(Object)}) or during iteration (using the {@link #referenceIterator()} resp. {@link
* #references()} method).
*
* The validity of references is retained through all operations on the collection, except for those that cause removal
* of the respective elements.
*
* @param
* element class
*
* @author Malte Isberner
*/
@ParametersAreNonnullByDefault
public interface SmartCollection extends Collection {
/**
* Retrieves an element by its reference.
*
* If the reference belongs to another collection, the behavior is undefined.
*
* @param ref
* the element's reference.
*
* @return the element.
*/
@Nullable
E get(ElementReference ref);
/**
* Adds an element to the collection, returning a reference to the newly added element. If the collection does not
* support containing the same element multiple times, a reference to the previously existing element is returned.
*
* @param elem
* the element to be added.
*
* @return a reference to this element in the collection.
*/
@Nonnull
ElementReference referencedAdd(@Nullable E elem);
/**
* Removes an element (by its reference) from the collection.
*
* If the reference does not belong to this collection, the behavior is undefined.
*
* @param elem
* the reference to the element to be removed.
*/
void remove(ElementReference elem);
/**
* This function is deprecated and should not be used, in favor of the removal by reference {@link
* #remove(ElementReference)}.
*
* @see Collection#remove(Object)
*/
@Deprecated
@Override
boolean remove(@Nullable Object element);
/**
* Retrieves an arbitrary element from the collection. If the collection is empty, a {@link NoSuchElementException}
* is thrown
*
* @return an arbitrary element from the collection
*/
@Nullable
E choose() throws NoSuchElementException;
/**
* Retrieves the reference to an arbitrary element from the collection. If the collection is empty, a {@link
* NoSuchElementException} is thrown.
*
* @return the reference to an arbitrary element in the collection
*/
@Nonnull
ElementReference chooseRef();
/**
* Retrieves an iterator for iterating over the references of elements in this collection.
*
* @return the reference iterator.
*/
@Nonnull
Iterator referenceIterator();
/**
* This is a method provided for convenience, which allows iterating over the element references using a
* foreach-style for-loop.
*
* @return an {@link Iterable} with the above {@link #referenceIterator()} as its iterator.
*/
@Nonnull
Iterable references();
/**
* Adds all elements from a given iterable. Note that this may be inefficient, compared to adding a {@link
* Collection}, because the number of elements to be added is not known a priori.
*
* @param iterable
* the iterable of elements to add.
*/
void addAll(Iterable iterable);
/**
* Adds all elements from the specified array.
*
* @param
* array element class, may be a subclass of E.
* @param array
* the array of elements to be added.
*/
void addAll(T[] array);
/**
* Replaces the element referenced by the given reference with the specified element.
*
* @param ref
* the reference of the element to be replaced.
* @param newElement
* the replacement.
*/
void replace(ElementReference ref, @Nullable E newElement);
/**
* Retrieves the reference for a given element. If the element is not contained in the collection, null
* is returned.
*
* @param element
* the element to search for.
*
* @return the reference to this element, or null.
*/
ElementReference find(@Nullable Object element);
/**
* Quickly clears this collection. This method is supposed to perform the minimum amount of effort such that this
* collection is emptied, disregarding all other side-effects such as referencing or garbage collection issues.
*
* Depending on the implementation, this may be just the same as {@link Collection#clear()}. However, this could
* also have side-effects like hampering the garbage collection or such.
*
* After calling this method, even a call of the normal {@link Collection#clear()} is not guaranteed to fix all
* these issues. This can only be achieved by the method {@link #deepClear()} below.
*/
void quickClear();
/**
* Thoroughly clears the collection, fixing all issues that may have been caused by a call of the above {@link
* #quickClear()}.
*/
void deepClear();
}