juneau-core/juneau-marshall/src/main/java/org/apache/juneau/internal/MappedIterable.java

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package org.apache.juneau.internal;

import java.util.*;
import java.util.function.*;

/**
 * Combines an {@link Iterable} with a {@link Function} so that you can map
 * entries while iterating over them.
 *
 * @param <I> The unmapped type.
 * @param <E> The mapped type.
 */
public class MappedIterable<I,E> implements Iterable<E> {

	final Iterator<I> i;
	final Function<I,E> f;

	/**
	 * Constructor.
	 *
	 * @param i The original iterable being wrapped.
	 * @param f The function to use to convert from unmapped to mapped types.
	 */
	protected MappedIterable(Iterable<I> i, Function<I,E> f) {
		this.i = i.iterator();
		this.f = f;
	}

	/**
	 * Constructor.
	 *
	 * @param i The original iterable being wrapped.
	 * @param f The function to use to convert from unmapped to mapped types.
	 * @return A new iterable.
	 */
	public static <I,E> Iterable<E> of(Iterable<I> i, Function<I,E> f) {
		return new MappedIterable<>(i, f);
	}

	@Override
	public Iterator<E> iterator() {
		return new Iterator<E>() {
			@Override
			public boolean hasNext() {
				return i.hasNext();
			}
			@Override
			public E next() {
				return f.apply(i.next());
			}
		};
	}
}