Navigate through virtual worlds using Java 3D

import java.io.*;
/**
 *  This class is a specialization of the ElevationFile class created
 * specifically to load DEM format data from the USGS archives.
 *
 * @author  Mark Pendergast
 * @version 1.0 February 2003
 *  @see ElevationFile
 */
public class DemFile extends ElevationFile {
public static final int ARECORD_LENGTH = 1024; public static final int QUADRANGLE_NAME_LENGTH = 144; public static final int MIN_ARECORD_TOKENS = 39;
/**
*  Create DemFile object from data contained in specified file.
*
*  @param aFileName name of the DEM file to load. File name should be a
*  fully qualified file name.
*  @exception IllegalArgumnetException thrown whenever an invalid data
* file is given as an argument.
*/
public DemFile(String aFileName) throws IllegalArgumentException
{
  try{
      char[] Arecord = new char[ARECORD_LENGTH];
      fileName = new String(aFileName);
      FileReader file = new FileReader(fileName);   
      BufferedReader bReader = new BufferedReader(file);  
//
// Read and parse out A record.
//
      if(bReader.read(Arecord,0,ARECORD_LENGTH) == -1)
      {
       bReader.close();
       System.out.println("Invalid file format (bad arecord) : "+fileName);
       throw(new IllegalArgumentException("Invalid file format : "+ fileName));
     }
      quadrangleName = new String(Arecord, 0, QUADRANGLE_NAME_LENGTH);
      quadrangleName = quadrangleName.trim();
      minElevation = (int)parseDemDouble(new String(Arecord,738,24));
      maxElevation = (int)parseDemDouble(new String(Arecord,762,24));
      groundCoordinates.sw[GroundCoordinates.LONGITUDE] = 
         Math.abs(parseDemDouble(new String(Arecord,546,24)));
      groundCoordinates.sw[GroundCoordinates.LATITUDE] = 
         Math.abs(parseDemDouble(new String(Arecord,570,24)));
      groundCoordinates.nw[GroundCoordinates.LONGITUDE] = 
         Math.abs(parseDemDouble(new String(Arecord,594,24)));
      groundCoordinates.nw[GroundCoordinates.LATITUDE] =
         Math.abs(parseDemDouble(new String(Arecord,618,24)));
      groundCoordinates.ne[GroundCoordinates.LONGITUDE] =
         Math.abs(parseDemDouble(new String(Arecord,642,24)));
      groundCoordinates.ne[GroundCoordinates.LATITUDE] = 
         Math.abs(parseDemDouble(new String(Arecord,666,24)));
      groundCoordinates.se[GroundCoordinates.LONGITUDE] =
         Math.abs(parseDemDouble(new String(Arecord,690,24)));
      groundCoordinates.se[GroundCoordinates.LATITUDE] = 
         Math.abs(parseDemDouble(new String(Arecord,714,24)));
      nColumns = (int)parseDemDouble(new String(Arecord,858,6));
//
//  Use a StreamTokenizer to parse B records, one record for each column.
//  Set the StreamTokenizer to use a space a delimiter and convert all
//  tokens to strings.
//
    StreamTokenizer st = new StreamTokenizer(bReader); // Stream prepositioned to start of B record.
    st.resetSyntax();
    st.whitespaceChars(' ',' ');
    st.wordChars(' '+1,'z');
    for(int column = 0; column < nColumns; column++)
    {
     int ttype;
     double rowCoordinateLat, rowCoordinateLong;
     st.nextToken(); // Skip row ID.
     st.nextToken(); // Skip column ID.
     ttype = st.nextToken(); // Number of rows.
     nRows = (int)parseDemInt(st.sval);
     if(elevations == null) // Allocate array if necessary.
       elevations = new int[nRows][nColumns];
     for(int i=0; i < 6; i++)  // Skip 6 fields.
       st.nextToken();
     for(int row = 0; row<nRows; row++) // Read in elevation data.
     {
       st.nextToken();
       elevations[row][column]=  parseDemInt(st.sval);
     }
    }
    bReader.close();
   } // End try.
   catch(IOException e){
       System.out.println("IE Exception when loading from [" + fileName + "] error: " + 
       e.getMessage());
       throw new IllegalArgumentException("File I/O failure : "+fileName);
   }
   catch(NumberFormatException e){
       System.out.println("NumberFormat Exception when loading from [" + fileName + "] ");
       throw new IllegalArgumentException("Invalid file format : "+fileName);
   }
   System.gc();  // Clean out memory.
}
/**
 * This method parses a double from a string.  Note, DEM data uses
 * the old FORTRAN notation for storing doubles using a 'D' instead of an
 * 'E'.
 * @param in  string to parse
 * @return double value from string
 * @exception NumberFormatException thrown when string is not a valid double
 */
public double parseDemDouble(String in) throws NumberFormatException
{
  String st = in.replace('D','E');  // Convert FORTRAN format to modern.
  return Double.parseDouble(st.trim());
}
public int parseDemInt(String in) throws NumberFormatException
{
  String st = in.replace('D','E');  // Convert FORTRAN format to modern.
  return Integer.parseInt(st.trim());
}
}