Serialization and compression

Question

i have 3 big HashMap in a class.
i want to serialize/deserialize this class using Externization and compression.
if any one have good example to share.

Answer 1

You must remove the zos.close() line.
As I said, you are engaged in a space-time tradeoff: if you want speed don't compress; if you want to save space, compress. As this is the RMI group I assume this is going over a network so saving space will also save you tranmission time, but it will cost you compression and decompression time. Whether it is all really worth it is a moot point: you will have to measure and see. It is sounding to me as though maybe it isn't worth it.
If you really think 'use of Externalizable interface is slower than default Serializable interface' (I don't), you could also try making it Serializable with the Map fields marked as transient, as follows:
private void
readObject(ObjectInputStream objectInput) throws
IOException, ClassNotFoundException
objectInput.defaultReadObject();
GZIPInputStream zos = new GZIPInputStream(objectInput);
     ObjectInputStream oos = new ObjectInputStream(zos);
     map1 = (Map) oos.readObject();
     map2 = (Map) oos.readObject();
     map3 = (Map) oos.readObject();
private void writeObject(ObjectOutputStream objectOutput)
throws IOException
objectOutput.defaultWriteObject();
GZIPOutputStream zos = new GZIPOutputStream(objectOutput);
ObjectOutputStream oos = new ObjectOutputStream(zos);
     oos.writeObject(map1);
     oos.writeObject(map2);
     oos.writeObject(map3);
     zos.finish();
}Alternatively get rid of all this and construct your outer ObjectOutputStream around a GZipOutputStream, and your outer ObjectInputStream around a GZipInputStream. If you're doing RMI this is not possible: there is a solution involving a client socket factory but it's pretty clumsy.