EmptyDocIdSet.java

package com.browseengine.bobo.docidset;

import java.io.IOException;

import org.apache.lucene.search.DocIdSetIterator;

public final class EmptyDocIdSet extends RandomAccessDocIdSet {
  private static EmptyDocIdSet SINGLETON = new EmptyDocIdSet();

  private static class EmptyDocIdSetIterator extends DocIdSetIterator {
    @Override
    public int docID() {
      return -1;
    }

    @Override
    public int nextDoc() throws IOException {
      return DocIdSetIterator.NO_MORE_DOCS;
    }

    @Override
    public int advance(int target) throws IOException {
      return DocIdSetIterator.NO_MORE_DOCS;
    }

    @Override
    public long cost() {
      // TODO Auto-generated method stub
      return 0;
    }
  }

  private static EmptyDocIdSetIterator SINGLETON_ITERATOR = new EmptyDocIdSetIterator();

  private EmptyDocIdSet() {
  }

  public static EmptyDocIdSet getInstance() {
    return SINGLETON;
  }

  @Override
  public DocIdSetIterator iterator() {
    return SINGLETON_ITERATOR;
  }

  @Override
  public boolean get(int docId) {
    return false;
  }

}