A class to interate through the cross product of all of the pairs of values from iterators.

CrossProductIterator.java

import java.util.Iterator;

import com.google.common.collect.AbstractIterator;
import com.google.common.collect.Iterators;

/**
 */
public abstract class CrossProductIterator<A, B, C> extends AbstractIterator<A> {
  private Iterator<B> outer_;

  private B curOuter_;

  private Iterator<C> inner_;

  private final Iterable<C> suffixes_;

  public CrossProductIterator(final Iterable<B> prefixes, final Iterable<C> suffixes) {
    outer_ = prefixes.iterator();
    inner_ = Iterators.emptyIterator();
    suffixes_ = suffixes;
    curOuter_ = null;
  }

  @Override
  protected A computeNext() {
    while (true) {
      if (inner_.hasNext()) {
        return combiner(curOuter_, inner_.next());
      }

      if (outer_.hasNext()) {
        curOuter_ = outer_.next();
        inner_ = suffixes_.iterator();

      }
      else {
        return endOfData();
      }
    }
  }

  abstract A combiner(final B outer, final C inner);
}