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package sun.java2d;
This interface is used to track changes to the complex data of an
object that implements the StateTrackable interface.
The usage pattern for code accessing the trackable data is as follows:
StateTrackable trackedobject;
MyInfo cacheddata;
StateTracker cachetracker;
public synchronized MyInfo getInfoAbout(StateTrackable obj) {
if (trackedobject != obj || !cachetracker.isCurrent()) {
// Note: Always call getStateTracker() before
// caching any data about the objct...
cachetracker = obj.getStateTracker();
cacheddata = calculateInfoFrom(obj);
trackedobject = obj;
}
return cacheddata;
}
Note that the sample code above works correctly regardless of the State
of the complex data of the object, but it may be inefficient to store precalculated information about an object whose current State
is UNTRACKABLE
and it is unnecessary to perform the isCurrent
test for data whose current State
is IMMUTABLE
. Optimizations to the sample code for either or both of those terminal States may be of benefit for some use cases, but is left out of the example to reduce its complexity. See Also: Since: 1.7
/**
* This interface is used to track changes to the complex data of an
* object that implements the StateTrackable interface.
* <p>
* The usage pattern for code accessing the trackable data is as follows:
* <pre>
* StateTrackable trackedobject;
* MyInfo cacheddata;
* StateTracker cachetracker;
* public synchronized MyInfo getInfoAbout(StateTrackable obj) {
* if (trackedobject != obj || !cachetracker.isCurrent()) {
* // Note: Always call getStateTracker() before
* // caching any data about the objct...
* cachetracker = obj.getStateTracker();
* cacheddata = calculateInfoFrom(obj);
* trackedobject = obj;
* }
* return cacheddata;
* }
* </pre>
* Note that the sample code above works correctly regardless of the
* {@link StateTrackable.State State} of the complex data of the object,
* but it may be inefficient to store precalculated information about
* an object whose current {@link StateTrackable.State State} is
* {@link StateTrackable.State#UNTRACKABLE UNTRACKABLE}
* and it is unnecessary to perform the {@link #isCurrent} test for
* data whose current {@link StateTrackable.State State} is
* {@link StateTrackable.State#IMMUTABLE IMMUTABLE}.
* Optimizations to the sample code for either or both of those terminal
* States may be of benefit for some use cases, but is left out of the
* example to reduce its complexity.
*
* @see StateTrackable.State
* @since 1.7
*/
public interface StateTracker {
An implementation of the StateTracker interface which always returns true. This implementation is useful for objects whose current State
is IMMUTABLE
. Since: 1.7
/**
* An implementation of the StateTracker interface which
* always returns true.
* This implementation is useful for objects whose current
* {@link StateTrackable.State State} is
* {@link StateTrackable.State#IMMUTABLE IMMUTABLE}.
* @since 1.7
*/
public StateTracker ALWAYS_CURRENT = new StateTracker() {
public boolean isCurrent() {
return true;
}
};
An implementation of the StateTracker interface which always returns false. This implementation is useful for objects whose current State
is UNTRACKABLE
. This implementation may also be useful for some objects whose current State
is DYNAMIC
. Since: 1.7
/**
* An implementation of the StateTracker interface which
* always returns false.
* This implementation is useful for objects whose current
* {@link StateTrackable.State State} is
* {@link StateTrackable.State#UNTRACKABLE UNTRACKABLE}.
* This implementation may also be useful for some objects
* whose current {@link StateTrackable.State State} is
* {@link StateTrackable.State#DYNAMIC DYNAMIC}.
* @since 1.7
*/
public StateTracker NEVER_CURRENT = new StateTracker() {
public boolean isCurrent() {
return false;
}
};
Returns true iff the contents of the complex data of the
associated StateTrackable object have not changed since
the time that this StateTracker was returned from its
getStateTracker() method.
See Also: - StateTrackable
Since: 1.7
/**
* Returns true iff the contents of the complex data of the
* associated StateTrackable object have not changed since
* the time that this StateTracker was returned from its
* getStateTracker() method.
* @see StateTrackable
* @since 1.7
*/
public boolean isCurrent();
}