ListMapValueIterator.java

package hunternif.mc.atlas.util;

import com.google.common.collect.Maps;

import java.util.Iterator;
import java.util.List;
import java.util.Map;

/**
 * Iterates over the values in a map of lists, similar to
 * {@link Maps#valueIterator}. This iterator will reflect changes made to the
 * map if map.values() does.
 * @author Hunternif
 */
public class ListMapValueIterator<E> implements Iterator<E> {
	private final Iterator<List<E>> valuesIter;
	private Iterator<E> nextListIter;
	private E next;
	private boolean immutable = false;
	
	public ListMapValueIterator(Map<?, List<E>> map) {
		valuesIter = map.values().iterator();
	}
	public ListMapValueIterator<E> setImmutable(boolean value) {
		this.immutable = value;
		return this;
	}
	
	@Override
	public boolean hasNext() {
		if (this.next == null) {
			this.next = findNext();
		}
		return next != null;
	}

	@Override
	public E next() {
		if (this.next == null) {
			this.next = findNext();
		}
		E next = this.next;
		this.next = null;
		return next;
	}

	@Override
	public void remove() {
		if (!immutable) {
			nextListIter.remove();
		}
	}
	
	private E findNext() {
		while (nextListIter == null
				|| !nextListIter.hasNext()) { // This condition allows to skip empty lists.
			if (valuesIter.hasNext()) {
				nextListIter = valuesIter.next().iterator();
			} else {
				return null;
			}
		}
		return nextListIter.next();
	}
}