Java Performance Tuning

Early and Late Initialization

The final two sections of this chapter discuss two seemingly opposing tuning techniques. Section 4.5.1 presents the technique of creating objects before they are needed. This technique is useful when a large number of objects need to be created at a time when CPU power is needed for other routines, and where those objects could feasibly be created earlier, at a time when there is ample spare CPU power.

Section 4.5.2, presents the technique of delaying object creation until the last possible moment. This technique is useful for avoiding unnecessary object creation when only a few objects are used although many possible objects can be created.

In fact, these techniques represent two sides of the same coin: moving object creation from one time to another. Preallocating moves object creation to a time earlier than you would normally create those objects; lazy initialization moves object creation to a later time (or never).

Preallocating Objects

There may be situations in which you cannot avoid creating particular objects in significant amounts: perhaps they are necessary for the application and no reasonable amount of tuning has managed to reduce the object-creation overhead for them. If the creation time has been identified as a bottleneck, it is possible that you can still create the objects, but move the creation time to a part of the application when more spare cycles are available or there is more flexibility in response times.

The idea here is to ...