leer registros de 40bytes

package accesoDatos;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

import javax.swing.JOptionPane;

public class AccesoAletario1 {
    static StringBuffer sb = new StringBuffer();

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int cont = 0;
        try (RandomAccessFile fichero = new RandomAccessFile("Aleatorio", "rw");) {
            final long SIZE = fichero.length();
            char dato;
            while(cont < SIZE) {
                for (int cont1 = 0; cont1 < 40; cont1 +=2) {
                    if ((dato = fichero.readChar()) == 0)
                        break;
                    else {
                        sb.append(dato);
                    }
                }
                sb.append("\n");
                cont += 40;
                fichero.seek(cont);
            }
            JOptionPane.showMessageDialog(null, sb.toString());
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}