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());
+    }
+
+}