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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.io;
import java.io.Closeable;
import java.util.Iterator;
import java.util.Objects;
import java.util.stream.Stream;
/**
* Wraps and presents a stream as a closable iterator resource that automatically closes itself when reaching the end
* of stream.
*
* @param <E> The stream and iterator type.
* @since 2.9.0
*/
final class StreamIterator<E> implements Iterator<E>, Closeable {
/**
* Wraps and presents a stream as a closable resource that automatically closes itself when reaching the end of
* stream.
* <h2>Warning</h2>
* <p>
* In order to close the stream, the call site MUST either close the stream it allocated OR call the iterator until
* the end.
* </p>
*
* @param <T> The stream and iterator type.
* @param stream The stream iterate.
* @return A new iterator.
*/
@SuppressWarnings("resource") // Caller MUST close or iterate to the end.
public static <T> Iterator<T> iterator(final Stream<T> stream) {
return new StreamIterator<>(stream).iterator;
}
private final Iterator<E> iterator;
private final Stream<E> stream;
private StreamIterator(final Stream<E> stream) {
this.stream = Objects.requireNonNull(stream, "stream");
this.iterator = stream.iterator();
}
/**
* Closes the underlying stream.
*/
@Override
public void close() {
stream.close();
}
@Override
public boolean hasNext() {
final boolean hasNext = iterator.hasNext();
if (!hasNext) {
close();
}
return hasNext;
}
@Override
public E next() {
final E next = iterator.next();
if (next == null) {
close();
}
return next;
}
}
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