Diff.java Source code

Introduction

Here is the source code for Diff.java

Source

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

public class Diff {
    public static void main(String args[]) {
        RandomAccessFile fh1 = null;
        RandomAccessFile fh2 = null;
        int bufsize; // size of smallest file
        long filesize1 = -1;
        long filesize2 = -1;
        byte buffer1[]; // the two file caches
        byte buffer2[];
        // check what you get as command-line arguments
        if (args.length == 0 || args[0].equals("?")) {
            System.err.println("USAGE: java Diff <file1> <file2> | ?");
            System.exit(0);
        }
        // open file ONE for reading
        try {
            fh1 = new RandomAccessFile(args[0], "r");
            filesize1 = fh1.length();
        } catch (IOException ioErr) {
            System.err.println("Could not find " + args[0]);
            System.err.println(ioErr);
            System.exit(100);
        }
        // open file TWO for reading
        try {
            fh2 = new RandomAccessFile(args[1], "r");
            filesize2 = fh2.length();
        } catch (IOException ioErr) {
            System.err.println("Could not find " + args[1]);
            System.err.println(ioErr);
            System.exit(100);
        }
        if (filesize1 != filesize2) {
            System.out.println("Files differ in size !");
            System.out.println("'" + args[0] + "' is " + filesize1 + " bytes");
            System.out.println("'" + args[1] + "' is " + filesize2 + " bytes");
        }
        // allocate two buffers large enough to hold entire files
        bufsize = (int) Math.min(filesize1, filesize2);
        buffer1 = new byte[bufsize];
        buffer2 = new byte[bufsize];
        try {
            fh1.readFully(buffer1, 0, bufsize);
            fh2.readFully(buffer2, 0, bufsize);

            for (int i = 0; i < bufsize; i++) {
                if (buffer1[i] != buffer2[i]) {
                    System.out.println("Files differ at offset " + i);
                    break;
                }
            }
        } catch (IOException ioErr) {
            System.err.println("ERROR: An exception occurred while processing the files");
            System.err.println(ioErr);
        } finally {
            try {
                fh1.close();
                fh2.close();
            } catch (IOException ignored) {
            }
        }
    }
}