/*
 * 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
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package org.apache.commons.collections4.collection;

import java.util.Collection;
import java.util.Iterator;

import org.apache.commons.collections4.Unmodifiable;
import org.apache.commons.collections4.iterators.UnmodifiableIterator;

Decorates another 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.

Type parameters:
  • <E> – the type of the elements in the collection
Since:3.0
/** * Decorates another {@link Collection} to ensure it can't be altered. * <p> * This class is Serializable from Commons Collections 3.1. * <p> * Attempts to modify it will result in an UnsupportedOperationException. * * @param <E> the type of the elements in the collection * @since 3.0 */
public final class UnmodifiableCollection<E> extends AbstractCollectionDecorator<E> implements Unmodifiable {
Serialization version
/** 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.

Params:
  • coll – the collection to decorate, must not be null
Type parameters:
  • <T> – the type of the elements in the collection
Throws:
Returns:an unmodifiable collection
Since:4.0
/** * Factory method to create an unmodifiable collection. * <p> * If the collection passed in is already unmodifiable, it is returned. * * @param <T> 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 <T> Collection<T> unmodifiableCollection(final Collection<? extends T> coll) { if (coll instanceof Unmodifiable) { @SuppressWarnings("unchecked") // safe to upcast final Collection<T> tmpColl = (Collection<T>) coll; return tmpColl; } return new UnmodifiableCollection<>(coll); } //-----------------------------------------------------------------------
Constructor that wraps (not copies).
Params:
  • coll – the collection to decorate, must not be null
Throws:
/** * 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<? extends E> coll) { super((Collection<E>) coll); } //----------------------------------------------------------------------- @Override public Iterator<E> iterator() { return UnmodifiableIterator.unmodifiableIterator(decorated().iterator()); } @Override public boolean add(final E object) { throw new UnsupportedOperationException(); } @Override public boolean addAll(final Collection<? extends E> coll) { throw new UnsupportedOperationException(); } @Override public void clear() { throw new UnsupportedOperationException(); } @Override public boolean remove(final Object object) { throw new UnsupportedOperationException(); } @Override public boolean removeAll(final Collection<?> coll) { throw new UnsupportedOperationException(); } @Override public boolean retainAll(final Collection<?> coll) { throw new UnsupportedOperationException(); } }