An Iterator that flattens iterating over a list of Iterators.

FlatIterator.java

import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * An Iterator that flattens iterating over a list of Iterators.
 *
 * Created by chris on 1/5/16.
 */
public class FlatIterator<Type> implements Iterator<Type> {

    private Iterator<Type> currentIterator;
    private Iterator<Iterator<Type>> iterator;
    private Type next;

    public FlatIterator(List<Iterator<Type>> iterators) {
        iterator = iterators.iterator();
        next = null;
        if (iterator.hasNext()) {
            currentIterator = iterator.next();
        }
    }

    @Override public boolean hasNext() {
        return next != null || setNext();
    }

    @Override public Type next() {
        if (!hasNext()) {
            throw new NoSuchElementException();
        }
        final Type type = next;
        next = null;
        return type;
    }

    @Override public void remove() {
        iterator.remove();
    }

    private boolean setNext() {
        if (next != null) {
            return true;
        } else {

            while (true) {

                if (currentIterator.hasNext()) {

                    next = currentIterator.next();
                    return true;
                } else {

                    if (iterator.hasNext()) {
                        currentIterator = iterator.next();
                    } else {
                        return false;
                    }
                }
            }
        }
    }
}