org.apache.openjpa.lib.util.collections.UnmodifiableCollection Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.openjpa.lib.util.collections;
import java.util.Collection;
import java.util.Iterator;
import java.util.function.Predicate;
/**
* Decorates another {@link Collection} to ensure it can't be altered.
*
* This class is Serializable from Commons Collections 3.1.
*
*
* Attempts to modify it will result in an UnsupportedOperationException.
*
*
* @param the type of the elements in the collection
* @since 3.0
*/
public final class UnmodifiableCollection
extends AbstractCollectionDecorator
implements Unmodifiable {
/** Serialization version */
private static final long serialVersionUID = -239892006883819945L;
/**
* Factory method to create an unmodifiable collection.
*
* If the collection passed in is already unmodifiable, it is returned.
*
* @param the type of the elements in the collection
* @param coll the collection to decorate, must not be null
* @return an unmodifiable collection
* @throws NullPointerException if collection is null
* @since 4.0
*/
public static Collection unmodifiableCollection(final Collection coll) {
if (coll instanceof Unmodifiable) {
@SuppressWarnings("unchecked") // safe to upcast
final Collection tmpColl = (Collection) coll;
return tmpColl;
}
return new UnmodifiableCollection<>(coll);
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies).
*
* @param coll the collection to decorate, must not be null
* @throws NullPointerException if collection is null
*/
@SuppressWarnings("unchecked") // safe to upcast
private UnmodifiableCollection(final Collection coll) {
super((Collection) coll);
}
//-----------------------------------------------------------------------
@Override
public Iterator iterator() {
return UnmodifiableIterator.unmodifiableIterator(decorated().iterator());
}
@Override
public boolean add(final E object) {
throw new UnsupportedOperationException();
}
@Override
public boolean addAll(final Collection coll) {
throw new UnsupportedOperationException();
}
@Override
public void clear() {
throw new UnsupportedOperationException();
}
@Override
public boolean remove(final Object object) {
throw new UnsupportedOperationException();
}
/**
* @since 4.4
*/
@Override
public boolean removeIf(final Predicate filter) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAll(final Collection coll) {
throw new UnsupportedOperationException();
}
@Override
public boolean retainAll(final Collection coll) {
throw new UnsupportedOperationException();
}
}