1 files changed, 57 insertions, 0 deletions
diff --git a/common/plugins/org.eclipse.jpt.common.utility/src/org/eclipse/jpt/common/utility/internal/reference/AbstractModifiableObjectReference.java b/common/plugins/org.eclipse.jpt.common.utility/src/org/eclipse/jpt/common/utility/internal/reference/AbstractModifiableObjectReference.java
new file mode 100644
index 0000000000..22af0639b6
--- /dev/null
+++ b/common/plugins/org.eclipse.jpt.common.utility/src/org/eclipse/jpt/common/utility/internal/reference/AbstractModifiableObjectReference.java
@@ -0,0 +1,57 @@
+/*******************************************************************************
+ * Copyright (c) 2013, 2015 Oracle. 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:
+ *     Oracle - initial API and implementation
+ ******************************************************************************/
+package org.eclipse.jpt.common.utility.internal.reference;
+
+import org.eclipse.jpt.common.utility.internal.ObjectTools;
+import org.eclipse.jpt.common.utility.reference.ModifiableObjectReference;
+
+/**
+ * Implement some of the methods in {@link ModifiableObjectReference} that can
+ * be defined in terms of the other methods.
+ * Subclasses need only implement<ul>
+ * <li>{@link #getValue()}
+ * <li>{@link #setValue(Object)}
+ * </ul>
+ * 
+ * @param <V> the type of the reference's value
+ */
+public abstract class AbstractModifiableObjectReference<V>
+	extends AbstractObjectReference<V>
+	implements ModifiableObjectReference<V>
+{
+	protected AbstractModifiableObjectReference() {
+		super();
+	}
+
+	public V setNull() {
+		return this.setValue(null);
+	}
+
+	public boolean commit(V newValue, V expectedValue) {
+		if (ObjectTools.equals(this.getValue(), expectedValue)) {
+			this.setValue(newValue);
+			return true;
+		}
+		return false;
+	}
+
+	public V swap(ModifiableObjectReference<V> other) {
+		if (other == this) {
+			return this.getValue();
+		}
+		V otherValue = other.getValue();
+		if (ObjectTools.equals(this.getValue(), otherValue)) {
+			return this.getValue();
+		}
+		other.setValue(this.getValue());
+		this.setValue(otherValue);
+		return otherValue;
+	}
+}