NPE during expiration check (fixes #842) (#843)

daemon/src/main/java/org/mvndaemon/mvnd/daemon/DaemonMemoryStatus.java

@@ -160,7 +160,7 @@ private void slideAndInsert(Deque<GcEvent> events, GcEvent event) {
     }
 
     public boolean isTrashing() {
-        if (strategy.heapUsageThreshold != 0 && strategy.thrashingThreshold != 0) {
+        if (strategy != null && strategy.heapUsageThreshold != 0 && strategy.thrashingThreshold != 0) {
             GcStats stats = heapStats();
             return stats != null
                     && stats.usedPercent >= strategy.heapUsageThreshold
@@ -171,7 +171,7 @@ public boolean isTrashing() {
     }
 
     public boolean isHeapSpaceExhausted() {
-        if (strategy.heapUsageThreshold != 0 && strategy.heapRateThreshold != 0) {
+        if (strategy != null && strategy.heapUsageThreshold != 0 && strategy.heapRateThreshold != 0) {
             GcStats stats = heapStats();
             return stats != null
                     && stats.usedPercent >= strategy.heapUsageThreshold
@@ -182,7 +182,7 @@ public boolean isHeapSpaceExhausted() {
     }
 
     public boolean isNonHeapSpaceExhausted() {
-        if (strategy.nonHeapUsageThreshold != 0) {
+        if (strategy != null && strategy.nonHeapUsageThreshold != 0) {
             GcStats stats = nonHeapStats();
             return stats != null && stats.usedPercent >= strategy.nonHeapUsageThreshold;
         } else {

daemon/src/test/java/org/mvndaemon/mvnd/daemon/DaemonMemoryStatusTest.java

@@ -0,0 +1,40 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+package org.mvndaemon.mvnd.daemon;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+public class DaemonMemoryStatusTest {
+
+    @Test
+    void testStrategy() {
+        ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();
+        try {
+            DaemonMemoryStatus status = new DaemonMemoryStatus(executor);
+            assertNotNull(status.strategy);
+        } finally {
+            executor.shutdownNow();
+        }
+    }
+}