InterleavedIterator.java

package com.outbrain.utils;

import java.util.Iterator;

public class InterleavedIterator<T> implements Iterator<T> {
  private Iterator<T> it1;
  private Iterator<T> it2;

  private boolean takeFirst;

  public InterleavedIterator(Iterator<T> it1, Iterator<T> it2) {
    this(it1, it2, true);
  }

  public InterleavedIterator(Iterator<T> it1, Iterator<T> it2, final boolean takeFirst) {
    this.it1 = it1;
    this.it2 = it2;
    this.takeFirst = takeFirst;
  }

  @Override
  public boolean hasNext() {
    return it1.hasNext() || it2.hasNext();
  }

  @Override
  public T next() {
    T res = null;
    if (takeFirst && it1.hasNext()) {
      res = it1.next();
      takeFirst = false;
    } else if (it2.hasNext()) {
      res = it2.next();
      takeFirst = true;
    } else if (it1.hasNext()) {
      res = it1.next();
    }
    return res;
  }
}