/*
* Copyright (c) Members of the EGEE Collaboration. 2006-2010.
* See http://www.eu-egee.org/partners/ for details on the copyright holders.
*
* 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 org.glite.authz.common.util;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import net.jcip.annotations.NotThreadSafe;
/**
* A list that is lazy initialized. This list takes very little memory when storing zero or one item.
*
* @param <ElementType> type of elements within the list
*/
@NotThreadSafe
public class LazyList<ElementType> implements List<ElementType>, Serializable {
/** Serial version UID. */
private static final long serialVersionUID = -7741904523916701817L;
/** Delegate list. */
private List<ElementType> delegate = Collections.emptyList();
/** {@inheritDoc} */
public boolean add(ElementType item) {
if (delegate.isEmpty()) {
delegate = Collections.singletonList(item);
return true;
} else {
delegate = buildList();
return delegate.add(item);
}
}
/** {@inheritDoc} */
public void add(int index, ElementType element) {
delegate = buildList();
delegate.add(index, element);
}
/** {@inheritDoc} */
public boolean addAll(Collection<? extends ElementType> collection) {
delegate = buildList();
return delegate.addAll(collection);
}
/** {@inheritDoc} */
public boolean addAll(int index, Collection<? extends ElementType> collection) {
delegate = buildList();
return delegate.addAll(index, collection);
}
/** {@inheritDoc} */
public void clear() {
delegate = Collections.emptyList();
}
/** {@inheritDoc} */
public boolean contains(Object element) {
return delegate.contains(element);
}
/** {@inheritDoc} */
public boolean containsAll(Collection<?> collections) {
return delegate.containsAll(collections);
}
/** {@inheritDoc} */
public ElementType get(int index) {
return delegate.get(index);
}
/** {@inheritDoc} */
public int indexOf(Object element) {
return delegate.indexOf(element);
}
/** {@inheritDoc} */
public boolean isEmpty() {
return delegate.isEmpty();
}
/** {@inheritDoc} */
public Iterator<ElementType> iterator() {
return delegate.iterator();
}
/** {@inheritDoc} */
public int lastIndexOf(Object element) {
return delegate.lastIndexOf(element);
}
/** {@inheritDoc} */
public ListIterator<ElementType> listIterator() {
return delegate.listIterator();
}
/** {@inheritDoc} */
public ListIterator<ElementType> listIterator(int index) {
return delegate.listIterator(index);
}
/** {@inheritDoc} */
public boolean remove(Object element) {
delegate = buildList();
return delegate.remove(element);
}
/** {@inheritDoc} */
public ElementType remove(int index) {
delegate = buildList();
return delegate.remove(index);
}
/** {@inheritDoc} */
public boolean removeAll(Collection<?> collection) {
delegate = buildList();
return delegate.removeAll(collection);
}
/** {@inheritDoc} */
public boolean retainAll(Collection<?> collection) {
delegate = buildList();
return delegate.retainAll(collection);
}
/** {@inheritDoc} */
public ElementType set(int index, ElementType element) {
delegate = buildList();
return delegate.set(index, element);
}
/** {@inheritDoc} */
public int size() {
return delegate.size();
}
/** {@inheritDoc} */
public List<ElementType> subList(int fromIndex, int toIndex) {
return delegate.subList(fromIndex, toIndex);
}
/** {@inheritDoc} */
public Object[] toArray() {
return delegate.toArray();
}
/** {@inheritDoc} */
public <T> T[] toArray(T[] type) {
return delegate.toArray(type);
}
/**
* Builds an appropriate delegate for this list.
*
* @return delegate for this list
*/
protected List<ElementType> buildList() {
if (delegate instanceof ArrayList) {
return delegate;
}
return new ArrayList<ElementType>(delegate);
}
/** {@inheritDoc} */
public String toString() {
return delegate.toString();
}
/** {@inheritDoc} */
public int hashCode() {
return delegate.hashCode();
}
/** {@inheritDoc} */
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null || this.getClass() != obj.getClass()) {
return false;
}
return delegate.equals(((LazyList<?>) obj).delegate);
}
}