/*
 * 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.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
/** * Decorates an iterator such that it cannot be modified. * <p> * Attempts to modify it will result in an UnsupportedOperationException. * * @since 3.0 */
public final class UnmodifiableIterator<E> implements Iterator<E>, Unmodifiable {
The iterator being decorated
/** The iterator being decorated */
private final Iterator<? extends E> iterator; //-----------------------------------------------------------------------
Decorates the specified iterator such that it cannot be modified.

If the iterator is already unmodifiable it is returned directly.

Params:
  • iterator – the iterator to decorate
Type parameters:
  • <E> – the element type
Throws:
Returns:a new unmodifiable 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) { if (iterator == null) { throw new NullPointerException("Iterator must not be null"); } if (iterator instanceof Unmodifiable) { @SuppressWarnings("unchecked") // safe to upcast final Iterator<E> tmpIterator = (Iterator<E>) iterator; return tmpIterator; } return new UnmodifiableIterator<>(iterator); } //-----------------------------------------------------------------------
Constructor.
Params:
  • iterator – the iterator to decorate
/** * Constructor. * * @param iterator the iterator to decorate */
private UnmodifiableIterator(final Iterator<? extends E> 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"); } }