| This interfaces identifies mutable objects capable of being used again
or repeatedly; once
Reusable.reset reset , reusable objects behave as if
they were brand-new.
Reusable instances should not allocate new internal objects after
creation except for the purpose of increasing their internal capacities.
In such case the new allocations have to be performed in the same memory
areas as the reusable objects themselves (necessary to avoid memory leaks
or memory clashes when running on
RTSJ VMs). For example:[code]
import javax.realtime.MemoryArea;
public class Targets implements Reusable {
private Target[] _targets = new Target[32];
private int _count;
public void add(Target target) {
if (_count >= _targets.length) capacityOverflow();
_targets[_count++] = target;
}
private void capacityOverflow() {
MemoryArea.getMemoryArea(this).executeInArea(new Runnable() {
public void run() {
Target[] tmp = new Target[_targets.length * 2];
System.arraycopy(_targets, 0, tmp, 0, _count);
_targets = tmp;
}
});
}
...
}[/code]
Instances of this class can safely reside in permanent memory
(e.g. static members) or be an integral part of a
higher level component. For example:[code]
public class XMLFormat {
// RTSJ Unsafe! Memory leaks (when entries removed) or IllegalAssignmentError (when new entries while in ScopedArea).
static HashMap ClassToFormat = HashMap();
// RTSJ safe! FastMap is Reusable. Removed entries are internally recycled, new entries are in ImmortalMemory.
static FastMap ClassToFormat = FastMap();
}[/code]
Reusable objects can also be allocated on the stack providing that
their
javolution.context.ObjectFactory factory cleanup
method calls the
Reusable.reset reset method. For example:[code]
public class Foo implements Reusable {
private static final ObjectFactory FACTORY = new ObjectFactory() {
protected Foo create() {
return new Foo();
}
protected void cleanup(Foo obj) {
obj.reset();
}
};
public static Foo newInstance() {
return FACTORY.object(); // On the "stack" when executing in a StackContext.
}
...
}[/code]
author:
Jean-Marie Dautelle
version:
3.7, January 1, 2006 |