Java Performance Tuning

Serialization

Objects are serialized in a number of situations in Java. The two main reasons to serialize objects are to transfer objects and to store them.

There are several ways to improve the performance of serialization and deserialization. First, fields that are transient do not get serialized, saving both space and time. You can consider implementing readObject() and writeObject() (see java.io.Serializable documentation) to override the default serialization routine; it may be that you can produce a faster serialization routine for your specific objects. If you need this degree of control, you are better off using the java.io.Externalizable interface (the reason is illustrated shortly). Overriding the default serialization routine in this way is generally only worth doing for large or frequently serialized objects. The tight control this gives you may also be necessary to correctly handle canonicalized objects (to ensure objects remain canonical when deserializing them).

To transfer objects across networks, it is worth compressing the serialized objects. For large amounts of data, the transfer overhead tends to swamp the costs of compressing and decompressing the data. For storing to disk, it is worth serializing multiple objects to different files rather than to one large file. The granularity of access to individual objects and subsets of objects is often improved as well.

It is also possible to serialize objects in a separate thread for storage and network transfers, ...