Create checksum for a zip file in Java

/*from   w  ww. j  a  v a 2  s .co m*/
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.zip.Adler32;
import java.util.zip.CheckedOutputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

public class Main {
  public static void main(String[] args) throws Exception {
    CheckedOutputStream checksum = new CheckedOutputStream(
        new FileOutputStream("data.zip"), new Adler32());
    ZipOutputStream zos = new ZipOutputStream(new BufferedOutputStream(checksum));

    int size = 0;
    byte[] buffer = new byte[1024];

    File dir = new File(".");
    String[] files = dir.list();

    for (int i = 0; i < files.length; i++) {
      System.out.println("Compressing: " + files[i]);
      FileInputStream fis = new FileInputStream(files[i]);
      ZipEntry zipEntry = new ZipEntry(files[i]);
      zos.putNextEntry(zipEntry);

      while ((size = fis.read(buffer, 0, buffer.length)) > 0) {
        zos.write(buffer, 0, size);
      }
      zos.closeEntry();
      fis.close();
    }
    zos.close();
    System.out.println("Checksum   : " + checksum.getChecksum().getValue());
  }
}