org.apache.commons.collections4.iterators.UnmodifiableIterator Maven / Gradle / Ivy
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/*
* 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 org.apache.commons.collections4.Unmodifiable;
/**
* Decorates an iterator such that it cannot be modified.
*
* Attempts to modify it will result in an UnsupportedOperationException.
*
*
* @since 3.0
*/
public final class UnmodifiableIterator implements Iterator, Unmodifiable {
/** The iterator being decorated */
private final Iterator iterator;
//-----------------------------------------------------------------------
/**
* Decorates the specified iterator such that it cannot be modified.
*
* If the iterator is already unmodifiable it is returned directly.
*
* @param the element type
* @param iterator the iterator to decorate
* @return a new unmodifiable iterator
* @throws NullPointerException if the iterator is null
*/
public static Iterator unmodifiableIterator(final Iterator iterator) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
if (iterator instanceof Unmodifiable) {
@SuppressWarnings("unchecked") // safe to upcast
final Iterator tmpIterator = (Iterator) iterator;
return tmpIterator;
}
return new UnmodifiableIterator<>(iterator);
}
//-----------------------------------------------------------------------
/**
* Constructor.
*
* @param iterator the iterator to decorate
*/
private UnmodifiableIterator(final Iterator iterator) {
super();
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");
}
}