001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4.set;
018
019import java.util.Collection;
020import java.util.Iterator;
021import java.util.Set;
022import java.util.function.Predicate;
023
024import org.apache.commons.collections4.Unmodifiable;
025import org.apache.commons.collections4.iterators.UnmodifiableIterator;
026
027/**
028 * Decorates another <code>Set</code> to ensure it can't be altered.
029 * <p>
030 * This class is Serializable from Commons Collections 3.1.
031 * </p>
032 * <p>
033 * Attempts to modify it will result in an UnsupportedOperationException.
034 * </p>
035 *
036 * @param <E> the type of the elements in this set
037 * @since 3.0
038 */
039public final class UnmodifiableSet<E>
040        extends AbstractSerializableSetDecorator<E>
041        implements Unmodifiable {
042
043    /** Serialization version */
044    private static final long serialVersionUID = 6499119872185240161L;
045
046    /**
047     * Factory method to create an unmodifiable set.
048     *
049     * @param <E> the element type
050     * @param set  the set to decorate, must not be null
051     * @return a new unmodifiable set
052     * @throws NullPointerException if set is null
053     * @since 4.0
054     */
055    public static <E> Set<E> unmodifiableSet(final Set<? extends E> set) {
056        if (set instanceof Unmodifiable) {
057            @SuppressWarnings("unchecked") // safe to upcast
058            final Set<E> tmpSet = (Set<E>) set;
059            return tmpSet;
060        }
061        return new UnmodifiableSet<>(set);
062    }
063
064    //-----------------------------------------------------------------------
065    /**
066     * Constructor that wraps (not copies).
067     *
068     * @param set  the set to decorate, must not be null
069     * @throws NullPointerException if set is null
070     */
071    @SuppressWarnings("unchecked") // safe to upcast
072    private UnmodifiableSet(final Set<? extends E> set) {
073        super((Set<E>) set);
074    }
075
076    //-----------------------------------------------------------------------
077    @Override
078    public Iterator<E> iterator() {
079        return UnmodifiableIterator.unmodifiableIterator(decorated().iterator());
080    }
081
082    @Override
083    public boolean add(final E object) {
084        throw new UnsupportedOperationException();
085    }
086
087    @Override
088    public boolean addAll(final Collection<? extends E> coll) {
089        throw new UnsupportedOperationException();
090    }
091
092    @Override
093    public void clear() {
094        throw new UnsupportedOperationException();
095    }
096
097    @Override
098    public boolean remove(final Object object) {
099        throw new UnsupportedOperationException();
100    }
101
102    /**
103     * @since 4.4
104     */
105    @Override
106    public boolean removeIf(Predicate<? super E> filter) {
107        throw new UnsupportedOperationException();
108    }
109
110    @Override
111    public boolean removeAll(final Collection<?> coll) {
112        throw new UnsupportedOperationException();
113    }
114
115    @Override
116    public boolean retainAll(final Collection<?> coll) {
117        throw new UnsupportedOperationException();
118    }
119
120}