The Best Way of Working with Zip Files in Java

Finally I found the best way of working with zip files in Java :)

In one of my hobby projects I need to work intensively with compressed files (mainly zip files). My first approach was to use the java.util.zip package, but was too slow. So I started looking for other options.

My second approach was to create a wrapper for the 7zip executable (so I could have cross-platform support). This approach was much better, from a performance point of view, but to retrieve any info I needed to parse console output and solve a lot of problems with the java.lang.Runtime class.

Today I've finally found the best solution .... but before some really simple comparations:

	java.util.zip	Home Made 7zip.exe Wrapper	"Best Solution"
Extract All	12203	4109	4094
Get Number of Elements	4000	4109	78

• All the measurements are in milliseconds
• The test was done with a 104MB zip file containing 110 jpg files.
• The "Get Number of Elements" with the "Home made Wrapper" is also done extracting everything and counting the number of files (I'm sorry I was a bit lazy here)

I don't think that I need to add too much to these numbers. The integrated Java zip package is nice, but painfully slow.

And finally is time to show the "Best Solution" and an example comparing it with the Java zip code ;)

The winner is "7-Zip-JBinding" and has they explain in their website:

7-Zip-JBinding is a java wrapper for 7-Zip C++ library. It allows extraction of many archive formats using a very fast native library directly from java through JNI.

Get the Number of files using java.util.zip

    static public int getSize(File file) {
   ZipFile zf = null;
   int total = -1;

   try {
       zf = new ZipFile(file);
       total = 0;
       for (Enumeration e = zf.entries(); e.hasMoreElements();) {
           e.nextElement();
           total++;
       }
       zf.close();
   } catch (ZipException ex) {
       Logger.getLogger(Zip.class.getName()).log(Level.SEVERE, null, ex);
   } catch (IOException ex) {
       Logger.getLogger(Zip.class.getName()).log(Level.SEVERE, null, ex);
   }

   return total;
}

And the same with 7-Zip-JBinding

public int getSize (File file) {
    RandomAccessFile randomAccessFile = null;
    ISevenZipInArchive inArchive = null;
    int total = -1;
    try {
        randomAccessFile = new RandomAccessFile(file.getAbsolutePath(), "r");
        inArchive = SevenZip.openInArchive(null, // autodetect archive type
                new RandomAccessFileInStream(randomAccessFile));

        total = inArchive.getNumberOfItems();

    } catch (Exception e) {
        System.err.println("Error occurs: " + e);
        System.exit(1);
    } finally {
        if (inArchive != null) {
            try {
                inArchive.close();
            } catch (SevenZipException e) {
                System.err.println("Error closing archive: " + e);
            }
        }
        if (randomAccessFile != null) {
            try {
                randomAccessFile.close();
            } catch (IOException e) {
                System.err.println("Error closing file: " + e);
            }
        }
    }

    return total;
}

As you can see the code is quite similar, but the performance is quite different.

See you.