Binary03.java

/*
    Binary03.java
    David Klick
    2005-01-26

Writes and then reads binary data in a file.
    This program demonstrates how to seek to a particular record.
*/

import java.io.*;

class MyRecord {
    public int n;
    public double x, y, z;
    public final int SIZE = 28;
    public void write(RandomAccessFile f, int recno) throws IOException {
        f.seek(recno * SIZE);
        f.writeInt(n);
        f.writeDouble(x);
        f.writeDouble(y);
        f.writeDouble(z);
    }
    public void read(RandomAccessFile f, int recno) throws IOException {
        f.seek(recno * SIZE);
        n = f.readInt();
        x = f.readDouble();
        y = f.readDouble();
        z = f.readDouble();
    }
    public String toString() {
        return "n = " + n + ", x = " + x + ", y = " + y + ", z = " + z;
    }
}

public class Binary03 {
    public static void main(String[] args) throws IOException {
        String filename = "Binary02.dat";
        RandomAccessFile file = new RandomAccessFile(filename, "rw");
        MyRecord tmp = new MyRecord();

// initialize array of records
       for (int i=0; i<10; i++) {
           tmp.n = i * 2;
           tmp.x = i * 1.1;
           tmp.y = i * 2.2;
           tmp.z = 100.0 - i * 3.3;
           tmp.write(file, i);
       }

// read data from file
       System.out.println("Data read from file:");
       for (int i=0; i<10; i++) {
           tmp.read(file, i);
           System.out.println(i + ": " + tmp);
       }
       file.close();
    }
}