YARN-11577. Fix CheckStyle.

Author: slfan1989

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/src/test/java/org/apache/hadoop/yarn/server/router/subcluster/capacity/TestYarnFederationWithCapacityScheduler.java

@@ -245,7 +245,7 @@ public void testNodesLost() throws Exception {
         assertNotNull(nodesInfo);
         ArrayList<NodeInfo> nodes = nodesInfo.getNodes();
         assertNotNull(nodes);
-        return (0 == nodes.size());
+        return nodes.isEmpty();
       } catch (Exception e) {
         return false;
       }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/src/test/java/org/apache/hadoop/yarn/server/router/subcluster/fair/TestYarnFederationWithFairScheduler.java

@@ -250,7 +250,7 @@ public void testNodesLost() throws Exception {
         assertNotNull(nodesInfo);
         ArrayList<NodeInfo> nodes = nodesInfo.getNodes();
         assertNotNull(nodes);
-        return (0 == nodes.size());
+        return nodes.isEmpty();
       } catch (Exception e) {
         return false;
       }