Added javadoc and eliminated unnecessary null checks.

examples/example-dualstack/src/main/java/io/grpc/examples/dualstack/DualStackClient.java

@@ -28,6 +28,14 @@
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
+/**
+ * A client that requests greetings from the {@link DualStackServer}.
+ * First it sends 5 requests using the default nameresolver and load balancer.
+ * Then it sends 10 requests using the example nameresolver and round robin load balancer.  These
+ * requests are evenly distributed among the 3 servers rather than favoring the server listening
+ * on both addresses because the ExampleDualStackNameResolver groups the 3 servers as 3 endpoints
+ * each with 2 addresses.
+ */
 public class DualStackClient {
     public static final String channelTarget = "example:///lb.example.grpc.io";
     private static final Logger logger = Logger.getLogger(DualStackClient.class.getName());

examples/example-dualstack/src/main/java/io/grpc/examples/dualstack/DualStackServer.java

@@ -30,6 +30,11 @@
 import java.util.concurrent.TimeUnit;
 import java.util.logging.Logger;
 
+/**
+ * Starts 3 different greeter services each on its own port, but all for localhost.
+ * The first service listens on both IPv4 and IPv6,
+ * the second on just IPv4, and the third on just IPv6.
+ */
 public class DualStackServer {
     private static final Logger logger = Logger.getLogger(DualStackServer.class.getName());
     private List<Server> servers;
@@ -89,17 +94,13 @@ private void start() throws IOException {
 
     private void stop() throws InterruptedException {
         for (Server server : servers) {
-            if (server != null) {
-                server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
-            }
+            server.shutdown().awaitTermination(30, TimeUnit.SECONDS);
         }
     }
 
     private void blockUntilShutdown() throws InterruptedException {
         for (Server server : servers) {
-            if (server != null) {
-                server.awaitTermination();
-            }
+            server.awaitTermination();
         }
     }
 

examples/example-dualstack/src/main/java/io/grpc/examples/dualstack/ExampleDualStackNameResolver.java

@@ -28,6 +28,10 @@
 import java.util.List;
 import java.util.stream.Collectors;
 
+/**
+ * A fake name resolver that resolves to a hard-coded list of 3 endpoints (EquivalentAddressGropu)
+ * each with 2 addresses (one IPv4 and one IPv6).
+ */
 public class ExampleDualStackNameResolver extends NameResolver {
     static public final int[] SERVER_PORTS = {50051, 50052, 50053};