Reading a Field in a Binary File

[janakiram.attuluri]

Hi All,

I have a binary file to read which contains the fields i specified in FileStructure. I read tht using DataInputStream.

example i gave u only some fields but there are 150 fields r thr those r short int and char[] s.

wht is the way of reading tht. output should print the values of variables i specified in the constructor.

class FileStructure I used only for ur reference. data i hav to read from binary file.




Class FileStructure
{
short aaaaa;
short bbbbb;
int ccccc;
int ddddd;
int eeeee;
char[] ffffff[2];
short gggg;

public FileStructure()
{
aaaaa= 640;
bbbbb= 304044;
ccccc=0;
ddddd=0;
eeeee=0;
gggg=0;
}
}
public class ReadFile
{
public static void main(String args[])
{
File f=new File("C:\\Documents and \\VRP_U071201092710OSS00012.DAT");
FileInputStream in = new FileInputStream(f);
DataInputStream dataInputStream = new DataInputStream(in);

short s=dataInputStream.readShort();
short s1=dataInputStream.readShort();
// how to loop this thr r multiple short and ints and char[] are thr.
}
}

[roots]

Code:

public class FileStructure {
	public static void main(String[] args) throws Exception {
		Object data[] = new Object[150];
		
		for(int i = 0 ; i < 150 ; i ++){
			data[i] = (short)43 ; // It is just an example
			/*
			 * Autoboxing allows you to add any primitive char and bytes ... 
			 */
		}
		
		for(int i = 0 ; i < 150 ; i ++){
			if(data[i] instanceof Short ){
				System.out.println("Short Data :" + data[i]);
			}
			
			// Similarly you can check with other primitive Wrappers  ..
		}
	}
}

[janakiram.attuluri]

Hi,

I am able to read it in this way. But, i am not sure abt the program

I have to find a value in the binary file which is at 628th byte(short value) which is 0 i have to change tht to 1 i did tht. now i need to write tht back to the same file in a binary format how to do tht?

please help me


import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.nio.ByteOrder;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;



public class ReadBinaryBuffer
{
public static void main(String args[])
{
try {
File file = new File("C:\\Documents and Settings\\jattulu\\files\\VRP_U071201092710OSS0001 2.DAT");
FileInputStream fin = new FileInputStream(file);
FileChannel fc = fin.getChannel();
ByteBuffer buf = ByteBuffer.allocateDirect((int)fc.size());
fc.read(buf);

byte buffer[] = new byte[(int)fc.size()];
//BIG_ENDIAN is the default
buf.order(ByteOrder.LITTLE_ENDIAN);
buf.rewind();
buf.get(buffer);
ByteArrayInputStream bin = new ByteArrayInputStream(buffer);
BufferedReader reader = new BufferedReader(new InputStreamReader(bin));



DataInputStream stream = new DataInputStream(bin);
buf.position(628);

short s=buf.getShort();
System.out.println("cocot_ind value:"+s);
if(s==0)
{

buf.putShort(628,(short)1);
}


buf.position(628);

short s1=buf.getShort();
System.out.println("cocot_ind value after change:"+s1);



}
catch (Exception e) {
e.printStackTrace();
}




}

}