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-rw-r--r--policy-utils/src/main/java/org/onap/policy/drools/utils/Reference.java72
-rw-r--r--policy-utils/src/test/java/org/onap/policy/drools/utils/ReferenceTest.java84
2 files changed, 156 insertions, 0 deletions
diff --git a/policy-utils/src/main/java/org/onap/policy/drools/utils/Reference.java b/policy-utils/src/main/java/org/onap/policy/drools/utils/Reference.java
new file mode 100644
index 00000000..0c4155fe
--- /dev/null
+++ b/policy-utils/src/main/java/org/onap/policy/drools/utils/Reference.java
@@ -0,0 +1,72 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * Copyright (C) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.drools.utils;
+
+/**
+ * Reference to an object. Used within functional methods, where thread-safety is not
+ * required.
+ *
+ * @param <T> type of object contained within the reference
+ */
+public class Reference<T> {
+ private T value;
+
+ /**
+ *
+ * @param value
+ */
+ public Reference(T value) {
+ this.value = value;
+ }
+
+ /**
+ * @return the current value
+ */
+ public final T get() {
+ return value;
+ }
+
+ /**
+ * Sets the reference to point to a new value.
+ *
+ * @param newValue
+ */
+ public final void set(T newValue) {
+ this.value = newValue;
+ }
+
+ /**
+ * Sets the value to a new value, if the value is currently the same as the old value.
+ *
+ * @param oldValue
+ * @param newValue
+ * @return {@code true} if the value was updated, {@code false} otherwise
+ */
+ public boolean compareAndSet(T oldValue, T newValue) {
+ if (value == oldValue) {
+ value = newValue;
+ return true;
+
+ } else {
+ return false;
+ }
+ }
+}
diff --git a/policy-utils/src/test/java/org/onap/policy/drools/utils/ReferenceTest.java b/policy-utils/src/test/java/org/onap/policy/drools/utils/ReferenceTest.java
new file mode 100644
index 00000000..1d6b111a
--- /dev/null
+++ b/policy-utils/src/test/java/org/onap/policy/drools/utils/ReferenceTest.java
@@ -0,0 +1,84 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * Copyright (C) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.drools.utils;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+import org.junit.Test;
+import org.onap.policy.drools.utils.Reference;
+
+public class ReferenceTest {
+
+ @Test
+ public void testReference() {
+ Reference<Integer> val = new Reference<>(null);
+ assertNull(val.get());
+
+ val = new Reference<>(10);
+ assertEquals(10, val.get().intValue());
+ }
+
+ @Test
+ public void testGet_testSet() {
+ Reference<Integer> val = new Reference<>(null);
+ assertNull(val.get());
+
+ val.set(20);
+ assertEquals(20, val.get().intValue());
+
+ val.set(30);
+ assertEquals(30, val.get().intValue());
+ }
+
+ @Test
+ public void testCompareAndSet() {
+ Reference<Integer> val = new Reference<>(null);
+
+ Integer v = 100;
+
+ // try an incorrect value - should fail and leave value unchanged
+ assertFalse(val.compareAndSet(500, v));
+ assertNull(val.get());
+
+ assertTrue(val.compareAndSet(null, v));
+ assertEquals(v, val.get());
+
+ // try an incorrect value - should fail and leave value unchanged
+ Integer v2 = 200;
+ assertFalse(val.compareAndSet(600, v2));
+ assertEquals(v, val.get());
+
+ // now try again, this time with the correct value
+ assertTrue(val.compareAndSet(v, v2));
+ assertEquals(v2, val.get());
+
+ Integer v3 = 300;
+ assertTrue(val.compareAndSet(v2, v3));
+ assertEquals(v3, val.get());
+
+ // try setting it back to null
+ assertTrue(val.compareAndSet(v3, null));
+ assertNull(val.get());
+ }
+
+}