Class ComputedSet<E>
- java.lang.Object
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- org.eclipse.core.databinding.observable.AbstractObservable
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- org.eclipse.core.databinding.observable.set.AbstractObservableSet<E>
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- org.eclipse.core.databinding.observable.set.ComputedSet<E>
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- Type Parameters:
E- the type of the elements in this set
- All Implemented Interfaces:
Iterable<E>,Collection<E>,Set<E>,IObservable,IObservableCollection<E>,IObservableSet<E>
public abstract class ComputedSet<E> extends AbstractObservableSet<E>
A lazily calculated set that automatically computes and registers listeners on its dependencies as long as all of its dependencies areIObservableobjects. Any change to one of the observable dependencies causes the set 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 set of all primes greater than 1 and less than the value of an
IObservableValue<Integer>.final IObservableValue max = WritableValue.withValueType(Integer.TYPE); max.setValue(Integer.valueOf(0)); IObservableSet primes = new ComputedSet() { protected Set calculate() { int maxVal = ((Integer) max.getValue()).intValue(); Set result = new HashSet(); outer: for (int i = 2; i < maxVal; i++) { for (Iterator it = result.iterator(); it.hasNext();) { Integer knownPrime = (Integer) it.next(); if (i % knownPrime.intValue() == 0) continue outer; } result.add(Integer.valueOf(i)); } return result; } }; System.out.println(primes); // => "[]" max.setValue(Integer.valueOf(20)); System.out.println(primes); // => "[2, 3, 5, 7, 11, 13, 17, 19]"- Since:
- 1.2
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Constructor Summary
Constructors Constructor Description ComputedSet()Creates a computed set in the default realm and with an unknown (null) element type.ComputedSet(Object elementType)Creates a computed set in the default realm and with the given element type.ComputedSet(Realm realm)Creates a computed set in given realm and with an unknown (null) element type.ComputedSet(Realm realm, Object elementType)Creates a computed set in the given realm and with the given element type.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description voidaddChangeListener(IChangeListener listener)Adds the given change listener to the list of change listeners.protected voidaddListener(Object listenerType, IObservablesListener listener)voidaddSetChangeListener(ISetChangeListener<? super E> listener)protected abstract Set<E>calculate()Subclasses must override this method to calculate the set contents.protected Objectclone()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 intdoGetSize()protected voidfireEvent(ObservableEvent event)ObjectgetElementType()Returns the element type of this observable collection, ornullif this observable collection is untyped.RealmgetRealm()protected Set<E>getWrappedSet()protected booleanhasListeners()booleanisStale()Returns whether the state of this observable is stale and is expected to change soon.protected voidremoveListener(Object listenerType, IObservablesListener listener)-
Methods inherited from class org.eclipse.core.databinding.observable.set.AbstractObservableSet
add, addAll, clear, contains, containsAll, equals, fireChange, fireSetChange, firstListenerAdded, getterCalled, hashCode, isEmpty, iterator, lastListenerRemoved, remove, removeAll, removeSetChangeListener, retainAll, setStale, size, toArray, toArray, toString
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Methods inherited from class org.eclipse.core.databinding.observable.AbstractObservable
addDisposeListener, addStaleListener, checkRealm, fireStale, isDisposed, removeChangeListener, removeDisposeListener, removeStaleListener
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Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface java.util.Collection
parallelStream, removeIf, stream, toArray
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Methods inherited from interface org.eclipse.core.databinding.observable.IObservable
addDisposeListener, addStaleListener, getRealm, isDisposed, removeChangeListener, removeDisposeListener, removeStaleListener
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Methods inherited from interface java.util.Set
spliterator
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Constructor Detail
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ComputedSet
public ComputedSet()
Creates a computed set in the default realm and with an unknown (null) element type.
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ComputedSet
public ComputedSet(Object elementType)
Creates a computed set 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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ComputedSet
public ComputedSet(Realm realm)
Creates a computed set in given realm and with an unknown (null) element type.- Parameters:
realm- the realm
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Method Detail
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doGetSize
protected int doGetSize()
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getWrappedSet
protected Set<E> getWrappedSet()
- Specified by:
getWrappedSetin classAbstractObservableSet<E>
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calculate
protected abstract Set<E> calculate()
Subclasses must override this method to calculate the set contents. Any dependencies used to calculate the set must beIObservable, and implementers must use one of the interface methods tagged TrackedGetter for ComputedSet to recognize it as a dependency.- Returns:
- the object's set.
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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 classAbstractObservableSet<E>- Returns:
- Returns the stale state.
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getElementType
public Object getElementType()
Description copied from interface:IObservableCollectionReturns the element type of this observable collection, ornullif this observable collection is untyped.- Returns:
- the element type or
nullif untyped
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addChangeListener
public void addChangeListener(IChangeListener listener)
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 classAbstractObservable
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addSetChangeListener
public void addSetChangeListener(ISetChangeListener<? super E> listener)
- Specified by:
addSetChangeListenerin interfaceIObservableSet<E>- Overrides:
addSetChangeListenerin classAbstractObservableSet<E>
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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 classAbstractObservable
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addListener
protected void addListener(Object listenerType, IObservablesListener listener)
- Parameters:
listenerType-listener-
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removeListener
protected void removeListener(Object listenerType, IObservablesListener listener)
- Parameters:
listenerType-listener-
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hasListeners
protected boolean hasListeners()
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fireEvent
protected void fireEvent(ObservableEvent event)
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getRealm
public Realm getRealm()
- Returns:
- Returns the realm.
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clone
protected Object clone() throws CloneNotSupportedException
- Overrides:
clonein classObject- Throws:
CloneNotSupportedException
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