/*
* Copyright (c) 2013 Cisco Systems, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
package org.opendaylight.yangtools.util;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableCollection;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ImmutableSet.Builder;
import com.google.common.collect.Iterators;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import javax.annotation.Nonnull;
/**
* An unmodifiable view over a {@link Collection}. Unlike the view returned via
* {@link Collections#unmodifiableCollection(Collection)}, this class checks its
* argument to ensure multiple encapsulation does not occur.
*
*
This class checks
* the argument so it prevents multiple encapsulation. Subclasses of
* {@link ImmutableCollection} are also recognized and not encapsulated.
*
* @param the type of elements in this collection
*/
public final class UnmodifiableCollection implements Collection, Serializable {
private static final long serialVersionUID = 1L;
private static final Class> UNMODIFIABLE_COLLECTION_CLASS;
private static final Collection> SINGLETON_CLASSES;
static {
UNMODIFIABLE_COLLECTION_CLASS = Collections.unmodifiableCollection(new ArrayList<>()).getClass();
final Builder> b = ImmutableSet.builder();
b.add(Collections.singleton(null).getClass());
b.add(Collections.singletonList(null).getClass());
SINGLETON_CLASSES = b.build();
}
private final Collection delegate;
private UnmodifiableCollection(final Collection delegate) {
this.delegate = Preconditions.checkNotNull(delegate);
}
/**
* Create an unmodifiable view of the target collection. If the instance is known
* to be unmodifiable, that instance is returned.
*
* @param collection Target collection
* @return An unmodifiable view of the collection
*/
public static Collection create(@Nonnull final Collection collection) {
if (collection instanceof UnmodifiableCollection || collection instanceof ImmutableCollection
|| Collections.EMPTY_LIST == collection || Collections.EMPTY_SET == collection
|| UNMODIFIABLE_COLLECTION_CLASS.isInstance(collection)
|| SINGLETON_CLASSES.contains(collection.getClass())) {
return collection;
}
return new UnmodifiableCollection<>(collection);
}
@Nonnull
@Override
public Iterator iterator() {
return Iterators.unmodifiableIterator(delegate.iterator());
}
@Override
public int size() {
return delegate.size();
}
@Override
public boolean isEmpty() {
return delegate.isEmpty();
}
@Override
public boolean contains(final Object o) {
return delegate.contains(o);
}
@Override
public Object[] toArray() {
return delegate.toArray();
}
@Override
public T[] toArray(@Nonnull final T[] a) {
return delegate.toArray(a);
}
@Override
public boolean containsAll(@Nonnull final Collection> c) {
return delegate.containsAll(c);
}
@Override
public boolean add(final E e) {
throw new UnsupportedOperationException();
}
@Override
public boolean addAll(@Nonnull final Collection extends E> c) {
throw new UnsupportedOperationException();
}
@Override
public boolean remove(final Object o) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAll(@Nonnull final Collection> c) {
throw new UnsupportedOperationException();
}
@Override
public boolean retainAll(@Nonnull final Collection> c) {
throw new UnsupportedOperationException();
}
@Override
public void clear() {
throw new UnsupportedOperationException();
}
@Override
public String toString() {
return "UnmodifiableCollection{" + delegate + "}";
}
}