package util.word;/** * Copyright 2004 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;/** A TokenStream enumerates the sequence of tokens, either from  fields of a document or from query text.  <p>  This is an abstract class.  Concrete subclasses are:  <ul>  <li>{@link Tokenizer}, a TokenStream  whose input is a Reader; and  <li>{@link TokenFilter}, a TokenStream  whose input is another TokenStream.  </ul>  */public abstract class TokenStream {  /** Returns the next token in the stream, or null at EOS. */  public abstract Token next() throws IOException;  /** Releases resources associated with this stream. */  public void close() throws IOException {}}