Question

I have one file created by 7zip program. I used deflate method to compress it. Now I want to create the same archive (with the same MD5sum) in java. When I create zip file, I used the algorithm that I found on the Internet for example http://www.kodejava.org/examples/119.html but when I created zip file with this method the compressed size is higher than size of the uncompressed file so what is going on? This isn’t a very useful compression. So how I can create zip file that is exactly same as zip file that I created with 7zip program ? If it helps I have all information about zip file that I created in 7zip program.

Answer 1

// simplified code for zip creation in java

import java.io.*;
import java.util.zip.*;

public class ZipCreateExample {

    public static void main(String[] args) throws Exception {

        // input file 
        FileInputStream in = new FileInputStream("F:/sometxt.txt");

        // out put file 
        ZipOutputStream out = new ZipOutputStream(new FileOutputStream("F:/tmp.zip"));

        // name the file inside the zip  file 
        out.putNextEntry(new ZipEntry("zippedjava.txt")); 

        // buffer size
        byte[] b = new byte[1024];
        int count;

        while ((count = in.read(b)) > 0) {
            out.write(b, 0, count);
        }
        out.close();
        in.close();
    }
}