Append to jar file using java codings

Question

Hi,
I have codings which could create jar file and write datas in it. but i need to append datas to existing jar file using java codings.Here i have attached my codings which will write datas to new jar file. when ever i use this my existing contents gets overritten. wat can i add to this to append.
FileOutputStream stream = new FileOutputStream(archiveFile,true);// archive file is jar file name
     JarOutputStream out = new JarOutputStream(stream, new Manifest());
JarEntry jarAdd = new JarEntry(tobeJar.getName()); // tobejar is a file to write in jar.
jarAdd.setTime(tobeJar.lastModified());
               out.putNextEntry(jarAdd);
               // Write file to archive
               FileInputStream in = new FileInputStream(tobeJar);
               while (true) {
               int nRead = in.read(buffer, 0, buffer.length);
               if (nRead <= 0)
               break;
               out.write(buffer, 0, nRead);
               out.closeEntry();
out.close();

Answer 1

JarInputStream in = new JarInputStream(new FileInputStream(oldJarName), true); // oldJarName is the JAR that contains all the files we want to keep
JarOutputStream out = new JarOutputStream(new FileOutputStream(tempJarName)); // this is your "out" variable
// copy the files from the old JAR to the new, but don't close the new JAR yet
JarEntry inEnt;
while ((inEnt = in.getNextJarEntry()) != null) {
  JarEntry outEnt = new JarEntry(inEnt); // copy size, modification time etc.
  byte[] data = inEnt.getSize();
  in.read(data); // read data for this old entry
  in.closeEntry();
  out.putNextEntry(outEnt);
  out.write(data); // copy it to the new entry
  out.closeEntry();
// now write an entry for the file we want to append - this is the OP's code
JarEntry jarAdd = new JarEntry(tobeJar.getName()); // tobejar is a file to write in jar.
jarAdd.setTime(tobeJar.lastModified());
out.putNextEntry(jarAdd);
// Write file to archive
FileInputStream in = new FileInputStream(tobeJar);
while (true) {
int nRead = in.read(buffer, 0, buffer.length);
if (nRead <= 0)
break;
out.write(buffer, 0, nRead);
out.closeEntry();
// and *now* we close the new JAR file.
out.close();
// We then delete the old JAR file...
new File(oldJarName).delete();
// ... and rename the new JAR file to use the old one's name.
new File(tempJarName).renameTo(new File(oldJarName));