--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/org.eclipse.core.databinding.observable/src/org/eclipse/core/internal/databinding/observable/EmptyObservableSet.d	Tue Apr 21 10:55:51 2009 +0200
@@ -0,0 +1,176 @@
+/*******************************************************************************
+ * Copyright (c) 2006, 2008 IBM Corporation and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     IBM Corporation - initial API and implementation
+ *     Matthew Hall - bug 208332
+ *******************************************************************************/
+
+package org.eclipse.core.internal.databinding.observable;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.Set;
+
+import org.eclipse.core.databinding.observable.IChangeListener;
+import org.eclipse.core.databinding.observable.IStaleListener;
+import org.eclipse.core.databinding.observable.Realm;
+import org.eclipse.core.databinding.observable.set.IObservableSet;
+import org.eclipse.core.databinding.observable.set.ISetChangeListener;
+import org.eclipse.core.runtime.Assert;
+
+/**
+ * Singleton empty set
+ */
+public class EmptyObservableSet : IObservableSet {
+
+    private static final Set emptySet = Collections.EMPTY_SET;
+
+    private Realm realm;
+    private Object elementType;
+
+    /**
+     * Creates a singleton empty set. This set may be disposed multiple times
+     * without any side-effects.
+     * 
+     * @param realm
+     *            the realm of the constructed set
+     */
+    public this(Realm realm) {
+        this(realm, null);
+    }
+
+    /**
+     * Creates a singleton empty set. This set may be disposed multiple times
+     * without any side-effects.
+     * 
+     * @param realm
+     *            the realm of the constructed set
+     * @param elementType
+     *            the element type of the constructed set
+     * @since 1.1
+     */
+    public this(Realm realm, Object elementType) {
+        this.realm = realm;
+        this.elementType = elementType;
+    }
+
+    public void addSetChangeListener(ISetChangeListener listener) {
+    }
+
+    public void removeSetChangeListener(ISetChangeListener listener) {
+    }
+
+    public Object getElementType() {
+        return elementType;
+    }
+
+    public int size() {
+        checkRealm();
+        return 0;
+    }
+
+    private void checkRealm() {
+        Assert.isTrue(realm.isCurrent(),
+                "Observable cannot be accessed outside its realm"); //$NON-NLS-1$
+    }
+
+    public bool isEmpty() {
+        checkRealm();
+        return true;
+    }
+
+    public bool contains(Object o) {
+        checkRealm();
+        return false;
+    }
+
+    public Iterator iterator() {
+        checkRealm();
+        return emptySet.iterator();
+    }
+
+    public Object[] toArray() {
+        checkRealm();
+        return emptySet.toArray();
+    }
+
+    public Object[] toArray(Object[] a) {
+        return emptySet.toArray(a);
+    }
+
+    public bool add(Object o) {
+        throw new UnsupportedOperationException();
+    }
+
+    public bool remove(Object o) {
+        throw new UnsupportedOperationException();
+    }
+
+    public bool containsAll(Collection c) {
+        checkRealm();
+        return c.isEmpty();
+    }
+
+    public bool addAll(Collection c) {
+        throw new UnsupportedOperationException();
+    }
+
+    public bool retainAll(Collection c) {
+        throw new UnsupportedOperationException();
+    }
+
+    public bool removeAll(Collection c) {
+        throw new UnsupportedOperationException();
+    }
+
+    public void clear() {
+        throw new UnsupportedOperationException();
+    }
+
+    public void addChangeListener(IChangeListener listener) {
+    }
+
+    public void removeChangeListener(IChangeListener listener) {
+    }
+
+    public void addStaleListener(IStaleListener listener) {
+    }
+
+    public void removeStaleListener(IStaleListener listener) {
+    }
+
+    public bool isStale() {
+        checkRealm();
+        return false;
+    }
+
+    public void dispose() {
+    }
+
+    public Realm getRealm() {
+        return realm;
+    }
+
+    public override equals_t opEquals(Object obj) {
+        checkRealm();
+        if (obj is this)
+            return true;
+        if (obj is null)
+            return false;
+        if (!( null !is cast(Set)obj ))
+            return false;
+
+        return (cast(Set) obj).isEmpty();
+    }
+
+    public override hash_t toHash() {
+        checkRealm();
+        return 0;
+    }
+}