Skeleton Transducer

Here is the transducer (scanner) with some pieces missing. The nextToken() method is called by the application program each time it needs another token. We will fill it in later.

import java.io.*;

class WebScanner
{
  MyPushbackReader in;
  String token;        // The current token
  int    ich;          // input character as int
  char   ch;           // current input character

  WebScanner ( Reader rdr )
  {
    in = new _____________( rdr );
  }

  private boolean isWhiteSpace( char ch )
  {
    if ( ch == ____ || ch == ____ || ch == ____ || ch == ____ ) 
      return true;
    else
      return false;
  }

  String nextToken() throws IOException
  {  
    . . . . .
  } 

}

The application supplies the WebScanner constructor with a Reader (usually a FileReader). The application should not need to bother with details like pushing back characters, so it is up to WebScanner to construct a MyPushbackReader.

The isWhiteSpace() method returns true or false depending on whether the character is white space or not. The method is used by the scanner. (The static method Character.isWhiteSpace() does the same thing).