ResultMerger.java

package com.browseengine.bobo.util;

import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeMap;

public class ResultMerger {

  public static <T> Iterator<T> mergeResults(final Iterator<T>[] results,
      final Comparator<T> comparator) {

    return new Iterator<T>() {
      TreeMap<T, Iterator<T>> map = new TreeMap<T, Iterator<T>>(comparator);
      {
        for (Iterator<T> result : results) {
          if (result.hasNext()) {
            map.put(result.next(), result);
          }
        }
      }

      @Override
      public boolean hasNext() {
        return map.size() > 0;
      }

      @Override
      public T next() {
        T first = map.firstKey();
        Iterator<T> iter = map.remove(first);
        while (iter.hasNext()) {
          T next = iter.next();
          if (!map.containsKey(next)) {
            map.put(next, iter);
            break;
          }
        }
        return first;
      }

      @Override
      public void remove() {
        T first = map.firstKey();
        Iterator<T> iter = map.remove(first);
        while (iter.hasNext()) {
          T next = iter.next();
          if (!map.containsKey(next)) {
            map.put(next, iter);
            break;
          }
        }
      }
    };
  }
}