500: Sidetrip

You learned about the traditional approach in Segment 482 and you learned about the token approach in Segment 487.

To see how the more sophisticated approach is related to the traditional approach, you can study the following definition of MovieStreamTokenizer, which is derived from the program shown in Segment 486.

import java.io.*; 
public class MovieStreamTokenizer { 
 FileInputStream stream; 
 InputStreamReader reader; 
 BufferedReader buffer; 
 Movie movie; 
 int MORE = 0, EOF = 1; 
 public static void main(String argv[]) throws IOException { 
  MovieStreamTokenizer tokens = new MovieStreamTokenizer("input.data");  
  while(tokens.nextMovie() != tokens.EOF) { 
   Movie m = tokens.movie; 
   System.out.println("Rating: " + m.rating());        
  } 
 } 
 public MovieStreamTokenizer (String fileName) throws IOException { 
  stream = new FileInputStream("input.data");  
  reader = new InputStreamReader(stream); 
  buffer = new BufferedReader(reader);    
 } 
 public int nextMovie () throws IOException { 
  String line = buffer.readLine(); 
  if (line != null && !line.equals("")) { 
   line = line.trim(); 
   int nextSpace = line.indexOf(" "); 
   int x = Integer.parseInt(line.substring(0, nextSpace)); 
   line = line.substring(nextSpace).trim(); 
   nextSpace = line.indexOf(" "); 
   int y = Integer.parseInt(line.substring(0, nextSpace)); 
   line = line.substring(nextSpace).trim(); 
   int z = Integer.parseInt(line); 
   movie = new Movie(x, y, z); 
   return MORE; 
  } 
  stream.close(); 
  return EOF; 
 } 
} 

The MovieStreamTokenizer constructor assigns values to instance variables for the file input stream, the input-stream reader, and the buffered reader. Each call to nextMovie reads a line of text from the buffered reader, processes that line to produce the arguments needed by the Movie constructor, and returns the value of the MORE instance variable. If there are no more lines of text, then nextMovie returns the value of the EOF variable.

Thus, a MovieStreamTokenizer instance provides a stream of movie instances, accessible via the movie instance variable, just as an ordinary stream tokenizer provides a stream of strings and doubles, accessible via the nval and sval instance variables.