Class ComputedList<E>
java.lang.Object
java.util.AbstractCollection<E>
java.util.AbstractList<E>
org.eclipse.core.databinding.observable.list.AbstractObservableList<E>
org.eclipse.core.databinding.observable.list.ComputedList<E>
- Type Parameters:
E- the list element type
- All Implemented Interfaces:
Iterable<E>,Collection<E>,List<E>,SequencedCollection<E>,IObservable,IObservableCollection<E>,IObservableList<E>
A lazily calculated list that automatically computes and registers listeners
on its dependencies as long as all of its dependencies are
IObservable objects. Any change to one of the observable dependencies
causes the list to be recomputed.
This class is thread safe. All state accessing methods must be invoked from
the current realm. Methods for adding and removing
listeners may be invoked from any thread.
Example: compute the fibonacci sequence, up to as many elements as the value
of an IObservableValue < Integer >.
final IObservableValue count = WritableValue.withValueType(Integer.TYPE);
count.setValue(Integer.valueOf(0));
IObservableList fibonacci = new ComputedList() {
protected List calculate() {
int size = ((Integer) count.getValue()).intValue();
List result = new ArrayList();
for (int i = 0; i < size; i++) {
if (i == 0)
result.add(Integer.valueOf(0));
else if (i == 1)
result.add(Integer.valueOf(1));
else {
Integer left = (Integer) result.get(i - 2);
Integer right = (Integer) result.get(i - 1);
result.add(Integer.valueOf(left.intValue() + right.intValue()));
}
}
return result;
}
};
System.out.println(fibonacci); // => "[]"
count.setValue(Integer.valueOf(5));
System.out.println(fibonacci); // => "[0, 1, 1, 2, 3]"
- Since:
- 1.1
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Field Summary
Fields inherited from class java.util.AbstractList
modCount -
Constructor Summary
ConstructorsConstructorDescriptionCreates a computed list in the default realm and with an unknown (null) element type.ComputedList(Object elementType) Creates a computed list in the default realm and with the given element type.ComputedList(Realm realm) Creates a computed list in given realm and with an unknown (null) element type.ComputedList(Realm realm, Object elementType) Creates a computed list in the given realm and with the given element type. -
Method Summary
Modifier and TypeMethodDescriptionvoidaddChangeListener(IChangeListener listener) Adds the given change listener to the list of change listeners.voidaddListChangeListener(IListChangeListener<? super E> listener) Adds the given list change listener to the list of list change listeners.Subclasses must override this method to calculate the list contents.static <E> IObservableList<E> Factory method to createComputedListobjects in an easy manner.voiddispose()Disposes of this observable object, removing all listeners registered with this object, and all listeners this object might have registered on other objects.protected intget(int index) Returns the element type of this observable collection, ornullif this observable collection is untyped.booleanisStale()Returns whether the state of this observable is stale and is expected to change soon.Methods inherited from class org.eclipse.core.databinding.observable.list.AbstractObservableList
add, addAll, addAll, addDisposeListener, addStaleListener, checkRealm, contains, containsAll, equals, fireChange, fireListChange, fireStale, firstListenerAdded, getRealm, hashCode, hasListeners, indexOf, isDisposed, isEmpty, iterator, lastIndexOf, lastListenerRemoved, move, remove, removeAll, removeChangeListener, removeDisposeListener, removeListChangeListener, removeStaleListener, retainAll, size, toArray, toArrayMethods inherited from class java.util.AbstractList
add, clear, listIterator, listIterator, remove, removeRange, set, subListMethods inherited from class java.util.AbstractCollection
toStringMethods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, waitMethods inherited from interface java.util.Collection
parallelStream, removeIf, stream, toArrayMethods inherited from interface org.eclipse.core.databinding.observable.list.IObservableList
listIterator, listIterator, remove, set, subListMethods inherited from interface java.util.List
add, addFirst, addLast, clear, getFirst, getLast, removeFirst, removeLast, replaceAll, reversed, sort, spliterator
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Constructor Details
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ComputedList
public ComputedList()Creates a computed list in the default realm and with an unknown (null) element type. -
ComputedList
Creates a computed list in the default realm and with the given element type.- Parameters:
elementType- the element type, may benullto indicate unknown element type
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ComputedList
Creates a computed list in given realm and with an unknown (null) element type.- Parameters:
realm- the realm
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ComputedList
Creates a computed list in the given realm and with the given element type.- Parameters:
realm- the realmelementType- the element type, may benullto indicate unknown element type
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Method Details
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create
Factory method to createComputedListobjects in an easy manner.The created list has a null
IObservableList.getElementType().- Parameters:
supplier-Supplier, which is tracked usingObservableTrackerto find out observables it uses, in the same manner ascalculate().- Returns:
ComputedListwhose elements are computed using the givenSupplier.- Since:
- 1.12
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doGetSize
protected int doGetSize()- Specified by:
doGetSizein classAbstractObservableList<E>- Returns:
- the size
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get
- Specified by:
getin interfaceIObservableList<E>- Specified by:
getin interfaceList<E>- Specified by:
getin classAbstractList<E>
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calculate
Subclasses must override this method to calculate the list contents. Any dependencies used to calculate the list must beIObservable, and implementers must use one of the interface methods tagged TrackedGetter for ComputedList to recognize it as a dependency.- Returns:
- the object's list.
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isStale
public boolean isStale()Description copied from interface:IObservableReturns whether the state of this observable is stale and is expected to change soon. A non-stale observable that becomes stale will notify its stale listeners. A stale object that becomes non-stale does so by changing its state and notifying its change listeners, it does not notify its stale listeners about becoming non-stale. Clients that do not expect asynchronous changes may ignore staleness of observable objects.- Specified by:
isStalein interfaceIObservable- Overrides:
isStalein classAbstractObservableList<E>- Returns:
- true if this observable's state is stale and will change soon.
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getElementType
Description copied from interface:IObservableCollectionReturns the element type of this observable collection, ornullif this observable collection is untyped.- Returns:
- the type of the elements or
nullif untyped
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addChangeListener
Description copied from interface:IObservableAdds the given change listener to the list of change listeners. Change listeners are notified about changes of the state of this observable in a generic way, without specifying the change that happened. To get the changed state, a change listener needs to query for the current state of this observable.- Specified by:
addChangeListenerin interfaceIObservable- Overrides:
addChangeListenerin classAbstractObservableList<E>- Parameters:
listener- the listener to add; notnull
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addListChangeListener
Description copied from interface:IObservableListAdds the given list change listener to the list of list change listeners.- Specified by:
addListChangeListenerin interfaceIObservableList<E>- Overrides:
addListChangeListenerin classAbstractObservableList<E>- Parameters:
listener- the change listener to add; notnull
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dispose
public void dispose()Description copied from interface:IObservableDisposes of this observable object, removing all listeners registered with this object, and all listeners this object might have registered on other objects.- Specified by:
disposein interfaceIObservable- Overrides:
disposein classAbstractObservableList<E>
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