EmptySpans.java

package org.apache.lucene.search.spans;


/**
 * Copyright 2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import java.io.IOException;
import java.util.Set;
import org.apache.lucene.search.Explanation;

/**
 * Expert: An empty list of spans, suitable for ORing with other lists.
 */
public class EmptySpans implements Spans 
{
  /** Static instance; there's no need to ever create a new EmptySpans() */
  public static EmptySpans theInstance = new EmptySpans();

  /** Don't create a new instance... use {@link EmptySpans#theInstance}. */
  private EmptySpans() {
  }

  public boolean next()
    throws IOException 
  {
    return false;
  }

  public boolean skipTo(int target)
    throws IOException 
  {
    return false;
  }

  public int doc() {
    throw new UnsupportedOperationException();
  }

  public int start() {
    throw new UnsupportedOperationException();
  }

  public int end() {
    throw new UnsupportedOperationException();
  }

  public float score() {
    throw new UnsupportedOperationException();
  }

  public void collectTerms(Set terms) {
  }

  public Explanation explain() {
    throw new UnsupportedOperationException();
  }
}