基于管道过滤器的KWIC系统实现（2）

package lws;

abstract public class Filter implements Runnable{

  protected Pipe input_;
  protected Pipe output_;
  private boolean is_started_ = false;
 
  public Filter(Pipe input, Pipe output){
    input_ = input;
    output_ = output;
  }

  //to start a new thread to do the transform work
  public void start(){
    if(!is_started_){
      is_started_ = true;
      Thread thread = new Thread(this);
      thread.start();
    }
  }

  //to stop the running thread
  public void stop(){
    is_started_ = false;
  }

  //the method of the thread
  public void run(){
    transform();
  }

  //method to do the transform work of the current instance of Filter
  abstract protected void transform();

}

package lws;

import java.io.PipedReader;
import java.io.PipedWriter;
import java.io.IOException;

public class Pipe{

  private PipedReader reader_;
  private PipedWriter writer_;

  public Pipe() throws IOException{
    writer_ = new PipedWriter();
    reader_ = new PipedReader();
    writer_.connect(reader_);
  }

  public void write(int c) throws IOException{
    writer_.write(c);
  }

  public int read() throws IOException{
    return reader_.read();
  }

  public void closeWriter() throws IOException{
    writer_.flush();
    writer_.close();
  }

  public void closeReader() throws IOException{
    reader_.close();
  }

}