public class ZipUtil {
    private static void zipFiles(File targetDirectory, List<File> files) throws IOException {
        FileOutputStream fos = new FileOutputStream(targetDirectory.getPath() + ".zip");
        try{
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            try{
                ZipOutputStream zos = new ZipOutputStream(baos);
                try{
                    for (File file : files){
                        byte[] content = FileUtils.readFileToByteArray(file);
                        ZipEntry entry = new ZipEntry(file.getCanonicalPath().substring(targetDirectory.getCanonicalPath().length()+1,
                                file.getCanonicalPath().length()));
                        entry.setSize(content.length);
                        zos.putNextEntry(entry);
                        zos.write(content);
                        zos.closeEntry();
                    }
                }
                finally {
                    zos.flush();
                    zos.close();
                }
                baos.writeTo(fos);
            }
            finally {
                baos.flush();
                baos.close();
            }
        }
		finally {
            fos.flush();
            fos.close();
        }
    }