Random access files?

[jframe]

i was reading how to use random access files, but it says each field should be of the same length inorder for the seek() to be used. but we cannot keep the fields of fixed length, say names and addresses will be of different length for different records....and i wanted to use the random, but this is confusing?

also what i want is
like i have three fields, first is a serial number, second name and third is say address, how do i make this fixed lenght?
also when i will view this..i want to view them by serial number like when user puts 2 the record number 2 should show, like all the three fields of record 2. please help....

[Dillinger4]

I don't think that you would be able to use seek() unless the fields were of a fixed length in bytes. Each character is encoded as Unicode which is two bytes so going from character to character would be easy using readByte() but word to word would be impossible as all the fields would be different lengths.

For instance the following code would print out each character that is contained in the file to the console.

import java.io.*;
 
public class R{
 public static void main(String[] args){
   
  File f;
  RandomAccessFile raf = null;  
 
  try{
  f = new File("C:" + File.separator + "U.txt");
  raf = new RandomAccessFile(f,"r");
  }catch(IOException e){;}  

  char filechar = 0; 
 
  for(;;){
   try{
    System.out.print(filechar = (char) raf.readByte()); 
   }catch(IOException e){
      System.exit(0); 
   }
  }
 }
}

[Dillinger4]

You could use a StringTokenizer if you wanted to keep the fields on the same line in the file as the size of the field would have no effect since you are just tokenizing the words that are delimited by spaces.

 import java.io.*;
 import java.util.*; 
 
 public class R{
  public static void main(String[] args){
   
   File f;
   RandomAccessFile raf = null;  
   String s = null;
  
  try{
   f = new File("C:" + File.separator + "U.txt");
   raf = new RandomAccessFile(f,"r");
   s = raf.readLine();
  }catch(IOException e){;}  

  StringTokenizer st = new StringTokenizer(s);

  while(st.hasMoreTokens()){  
   System.out.print(st.nextToken());
   System.out.println(); 
   }
  }
 }

[Dillinger4]

Any luck?