Missing file for YARN-4580

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/policy/PriorityComparator.java

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+/**
+ * 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.apache.hadoop.yarn.server.resourcemanager.scheduler.policy;
+
+import java.util.Comparator;
+
+import org.apache.hadoop.yarn.api.records.Priority;
+
+/**
+ * A Comparator which orders SchedulableEntities by priority.
+ */
+public class PriorityComparator implements Comparator<SchedulableEntity> {
+
+  @Override
+  public int compare(SchedulableEntity se1, SchedulableEntity se2) {
+    Priority p1 = se1.getPriority();
+    Priority p2 = se2.getPriority();
+    if (p1 == null && p2 == null) {
+      return 0;
+    } else if (p1 == null) {
+      return -1;
+    } else if (p2 == null) {
+      return 1;
+    }
+    return p1.compareTo(p2);
+  }
+}