samples: use LinkedHashMap for ordered publish (#938)

* samples: use LinkedHashMap for ordered publish * also update resume publish sample

Author: anguillanneuf

samples/snippets/src/main/java/pubsub/PublishWithOrderingKeys.java

@@ -27,7 +27,7 @@
 import com.google.pubsub.v1.PubsubMessage;
 import com.google.pubsub.v1.TopicName;
 import java.io.IOException;
-import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
@@ -54,7 +54,7 @@ public static void publishWithOrderingKeysExample(String projectId, String topic
  .build();
 
  try {
- Map<String, String> messages = new HashMap<String, String>();
+ Map<String, String> messages = new LinkedHashMap<String, String>();
  messages.put("message1", "key1");
  messages.put("message2", "key2");
  messages.put("message3", "key1");

samples/snippets/src/main/java/pubsub/ResumePublishWithOrderingKeys.java

@@ -27,7 +27,7 @@
 import com.google.pubsub.v1.PubsubMessage;
 import com.google.pubsub.v1.TopicName;
 import java.io.IOException;
-import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
@@ -52,7 +52,7 @@ public static void resumePublishWithOrderingKeysExample(String projectId, String
  .build();
 
  try {
- Map<String, String> messages = new HashMap<String, String>();
+ Map<String, String> messages = new LinkedHashMap<String, String>();
  messages.put("message1", "key1");
  messages.put("message2", "key2");
  messages.put("message3", "key1");