Reading a Binary / Structured / Formated File Using JAVA

Javatm>> Sound Very easy. But Is it? Can you please provide an example? you can use file HisD6.dat for testing. Please note this file is structured binary data file. If you want you can build on CEHJ solution on previous solution. Or do you have a different approach?
Udana

Javatm>>
Thank for the effort and time. But I don’t think in this way we can achieve the way we want it. I’m not talking about simple text files. Please read the Following question if you like further details>>
. http://www.experts-exchange.com/Programming/Languages/Java/Q_22425473.html and
http://www.experts-exchange.com/Programming/Languages/Java/Q_22429751.html
 I used to study Java at University and did more than 4 related subjects. And haven’t touch java since I started my job in VB6 five yeas or so ago. Look what happened to me..:). So guess I know the basics.

I'll try to see your code but let us wait for the others for their comments I'm a work and need to get back. I'll get back to this once I have chance thanks.

I stumbled upon a link that you may want to try:
http://www.particle.kth.se/~lindsey/JavaCourse/Book/Part1/Java/Chapter09/fileBinaryIO.html

ok thanks Javatm. Liks are working fine, I just checked them. Im at work too but close to 4.30 now.. Will post additional comments tonight

>>Can we read the record at once? like it can be done in VB?

Practicably, no, since Java doesn't support pointers to records/structs

The best way to do this is in Java is to shift the paradigm somewhat so that you can serialize a random-access-enabled container of Java classes, such as List.

Is that possible?

Otherwise, you should use RandomAccessFile. You'd need to seek to offset o and read 56 floats, followed by 56 floats, followed ...

In this case we know the exact size of a record. So we might able to search through records and then use a different aproach to manupulate the file. may be we can write a mathematical equation repesent java array element then get the offset.

Say we have a huge file similar to HistD6.dat
How we read 2 or 4 continuos bytes from a any location in file? Say 10001,10002,10003,10004. ?

By the way by serialize did you mean something like this example? http://www.particle.kth.se/~lindsey/JavaCourse/Book/Part1/Java/Chapter09/objectIO.html  
<<^^ This is interesting.

But I might need more brains to work on this..... Too sleepy now.

>>How we read 2 or 4 continuos bytes from a any location in file? Say 10001,10002,10003,10004. ?

By using a RandomAccessFile

http://java.sun.com/javase/6/docs/api/java/io/RandomAccessFile.html

>>By the way by serialize did you mean something like this example?

Yes

Ok Guys I did a small program to Create objects and record it to File.
HistX Class Object..............

package ReadFilez;
import java.io.Serializable;

public class HistX implements Serializable{

      private float[] units=new float[381];

      private float[] sell=new float[381];

      private float[] cost=new float[381];

      private short[] prom=new short[381];

      public HistX() {
      }

      /**
       * @return the cost
       */
      public float[] getCost() {
            return cost;
      }

      /**
       * @param cost the cost to set
       */
      public void setCost(float[] cost) {
            this.cost = cost;
      }

      /**
       * @return the prom
       */
      public short[] getProm() {
            return prom;
      }

      /**
       * @param prom the prom to set
       */
      public void setProm(short[] prom) {
            this.prom = prom;
      }

      /**
       * @return the sell
       */
      public float[] getSell() {
            return sell;
      }

      /**
       * @param sell the sell to set
       */
      public void setSell(float[] sell) {
            this.sell = sell;
      }

      /**
       * @return the units
       */
      public float[] getUnits() {
            return units;
      }

      /**
       * @param units the units to set
       */
      public void setUnits(float[] units) {
            this.units = units;
      }
}

My test program

package ReadFilez;
import ReadFilez.HistX;
import java.io.*;
import java.util.*;
import java.lang.*;


public class Testy {

 public static void main (String arg[]) {
     short[] promX = new short[381];
     float[] sellX = new float[381];
     float[] costX = new float[381];
     float[] qntyX = new float[381];
     
     HistX[] hxxx = new HistX[100];
     HistX h1 = new HistX();
     File f = null;
     f = new File ("testy123.dat");
     for(int m=0; m<100; m++){
            for(int j=0; j<380; j++){
             promX[j]=(short)123;
             sellX[j]=(float)1.23;
             costX[j]=(float)0.123;
             qntyX[j]=(float)31.0;            
            }//for j
         
             h1.setUnits(qntyX);
             h1.setProm(promX);
             h1.setCost(costX);
             h1.setSell(sellX);
             
            hxxx[m]=h1;
           
     }//for m
    saveMyClass(hxxx,f);
   
    // did not test getMyClass

    getMyClass(8, f);
    getMyClass(88, f);
   
   
 }//main
 
   static public void saveMyClass (HistX[] hxxx1, File f1) {
    try{    
        FileOutputStream file_out = new FileOutputStream (f1);
        ObjectOutputStream obj_out_stream = new ObjectOutputStream (file_out);
        obj_out_stream.writeObject(hxxx1);
        obj_out_stream.close ();
       }
        catch (IOException e) {
            System.out.println ("IO exception = " + e );
        }

   }
// did not test getMyClass  
   static public HistX[] getMyClass (int location, File file) {
     //HistX[] hx = new HistX[100];
     //HistX h2 = new HistX();
        try{    
            FileInputStream file_in = new FileInputStream (file);
            ObjectInputStream[] obj_in_streamX = new ObjectInputStream[100];
            ObjectInputStream obj_in_stream = new ObjectInputStream (file_in);
            obj_in_streamX[2] = (obj_in_streamX) obj_in_stream.readObject();
           
            obj_in_stream.close ();
    return hx;
           }
        catch (IOException e) {
            System.out.println ("IO exception = " + e );
    }
  }
   
   
} // Testy

Now I can wrte History Object to a File. But Im not 100% sure whether its writing the correct information.
File wrting is arround 6kb, should be arround 500kb. (looks like its writing only one record of History)

I want to read the data I have writen. If can read the serialize data into an array I can access point. But I'm not good at this reading concept.
Can You guys please help me?
Udana

You need to serialize a collection of that class. Add instances to a List and then serialize the List

CEHJ>>
What do you mean by 'instances to a List'?

Add objects to the list.