| /* |
| * 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.commons.collections4.iterators; |
| |
| import java.util.Iterator; |
| import java.util.Objects; |
| |
| import org.apache.commons.collections4.Unmodifiable; |
| |
| /** |
| * Decorates an iterator such that it cannot be modified. |
| * <p> |
| * Attempts to modify it will result in an UnsupportedOperationException. |
| * </p> |
| * |
| * @param <E> the type of elements returned by this iterator. |
| * @since 3.0 |
| */ |
| public final class UnmodifiableIterator<E> implements Iterator<E>, Unmodifiable { |
| |
| /** The iterator being decorated */ |
| private final Iterator<? extends E> iterator; |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Decorates the specified iterator such that it cannot be modified. |
| * <p> |
| * If the iterator is already unmodifiable it is returned directly. |
| * |
| * @param <E> the element type |
| * @param iterator the iterator to decorate |
| * @return a new unmodifiable iterator |
| * @throws NullPointerException if the iterator is null |
| */ |
| public static <E> Iterator<E> unmodifiableIterator(final Iterator<? extends E> iterator) { |
| Objects.requireNonNull(iterator, "iterator"); |
| if (iterator instanceof Unmodifiable) { |
| @SuppressWarnings("unchecked") // safe to upcast |
| final Iterator<E> tmpIterator = (Iterator<E>) iterator; |
| return tmpIterator; |
| } |
| return new UnmodifiableIterator<>(iterator); |
| } |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Constructor. |
| * |
| * @param iterator the iterator to decorate |
| */ |
| private UnmodifiableIterator(final Iterator<? extends E> iterator) { |
| this.iterator = iterator; |
| } |
| |
| //----------------------------------------------------------------------- |
| @Override |
| public boolean hasNext() { |
| return iterator.hasNext(); |
| } |
| |
| @Override |
| public E next() { |
| return iterator.next(); |
| } |
| |
| @Override |
| public void remove() { |
| throw new UnsupportedOperationException("remove() is not supported"); |
| } |
| |
| } |