DDSJAVA — API Should Avoid Side-Effects, e.g. Remove Bucket Accessors

Description
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The DDS-PSM-Java provides bucket accessors that allow to "return" an object
by "filling" a method parameter.

As an example, for a property Foo there would be a method:

Foo f = // some foo
x.getFoo(f)

The rationale for this API is to avoid a defensive copy of Foo each time it is accessed.
However the cost of this "optimization" is an API that has side-effects everywhere,
with all the nasty implications of side-effects.

Resolution
---------------
The solution suggested to avoid bucket accessors and thus side-effects is to
rely as much as possible on immutable objects (e.g. value-types). This ensures
that (1) defensive copies are unnecessary since the attribute returned is immutable,
and (2) new objects are created when new values are required.

If properly designed (as shown on an issue posted on QoS and Policies) this approach
not only leads to a simpler and safer API, but it also leads to actually save memory in most
of the cases.

The only case where the suggested approach has a cost is when a property changes
very often. However, in many of these cases (often found in loops) the new JDK7
escape analysis will help greatly help in dealing with the potential garbage as it
will allocate these short-lived objects on the stack.

Proposed Resolution:
The solution suggested to avoid bucket accessors and thus side-effects is to rely as much as possible on immutable objects (e.g. value-types). This ensures that (1) defensive copies are unnecessary since the attribute returned is immutable, and (2) new objects are created when new values are required.
If properly designed (as shown on an issue posted on QoS and Policies) this approach not only leads to a simpler and safer API, but it also leads to actually save memory in most of the cases.
The only case where the suggested approach has a cost is when a property changes very often. However, in many of these cases (often found in loops) the new JDK7 escape analysis will help greatly help in dealing with the potential garbage as it will allocate these short-lived objects on the stack.