IteratorToEnumeration

package com.kaput.littlehelper;

import java.util.Enumeration;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Objects;

/**
 * Helper class to be able to use a{@link Iterator} (i.e. {@link java.util.stream.Stream}) with {@link Enumeration}.
 * This can be useful, i.e.:
 * <pre><code>
 * Stream<InputStream> inputStreams = Streams.of(...);
 * Enumeration<InputStream> inputStreamsEnumeration = new IteratorToEnumeration<>(inputStreams.iterator());
 * try (final SequenceInputStream sequenceInputStream = new SequenceInputStream(inputStreamsEnumeration)) {...}
 * </code></pre>
 *
 * @param <T> type of elements to iterate/enumerate over
 */
public class IteratorToEnumeration<T> implements Enumeration<T> {

    private final Iterator<T> iterator;

    /**
     * Constructor to pass the {@link Iterator} and yield an {@link Enumeration}.
     *
     * @param iterator iterator must not be null
     */
    public IteratorToEnumeration(final Iterator<T> iterator) {
        Objects.requireNonNull(iterator, "Iterator must not be null!");
        this.iterator = iterator;
    }

    @Override
    public boolean hasMoreElements() {
        return this.iterator.hasNext();
    }

    @Override
    public T nextElement() {
        if (!this.iterator.hasNext()) {
            throw new NoSuchElementException();
        }
        return this.iterator.next();
    }
}