Closing ZipOutputStream

You should close the FileOutputStream, not the ZipOutputStream, because the former is what actually consumes system resources.

File zipFile = new File("/tmp/example.zip");
FileOutputStream fos = null;
try
{
   fos = new FileOutputStream(zipFile);
   ZipOutputStream zos = new ZipOutputStream(fos);

   // ...

   zos.close();
}
catch (IOException ex)
{
   // log/report exception, then delete the invalid file
   IOUtils.closeQuietly(fos);
   zipFile.delete();
}
finally
{
   IOUtils.closeQuietly(fos);
}

The IOUtils class is found in Jakarta Commons IO. Using it means that you don't have to deal with the possible-but-rarely-useful IOException that can be thrown by close().

Instead of closing the stream only when things are added, what I did is a condition check to see if there was anything to zip, before running the zip code. This helped me to simplify the process and I think can be used in general to handle the "ZIP file must have at least one entry" problem. True that closing zos may throw other exceptions, but that is rare.

I think it is problem with Java, that doesn't handle the case when there are no files to zip.

i.e:

int itemsToAdd=0;
//....

if ( itemsToAdd > 0 ) {

    ZipOutputStream zos = new ZipOutputStream(file);
    try {
        //add files to zip
    }
    finally {
        zos.close();
    }
}

You should track if you added stuff the zip stream and close it only when things were added:

ZipOutputStream zos = null; 
OutputStream file = new FileOutputStream("...")
int itemsAdded=0;
try
{
    zos = new ZipOutputStream(file);
    //
    //..
    // itemsAdded++; 
}
finally
{
    if ( itemsAdded > 0 ) {
         zos.close();
    } else {
         file.close();
    }
}

of if you don't need the count just use a boolean flag.