[Java] Improve List Subjects

docker/java/build.gradle

@@ -5,15 +5,18 @@ plugins {
 repositories {
     mavenCentral()
     maven {
-        url "https://oss.sonatype.org/content/repositories/snapshots"
+        url "https://oss.sonatype.org/content/repositories/releases/"
+    }
+    maven {
+        url "https://oss.sonatype.org/content/repositories/snapshots/"
     }
 }
 
 dependencies {
     implementation 'io.nats:nkeys-java:2.0.1'
     implementation 'io.nats:jnats-json:2.0.0'
     implementation 'io.nats:jwt-java:2.0.0'
-    implementation 'io.nats:jnats:2.19.0'
+    implementation 'io.nats:jnats:2.19.2-SNAPSHOT'
 }
 
 apply plugin: 'java'

examples/jetstream/list-subjects/java/Main.java

@@ -4,10 +4,7 @@
 import io.nats.client.api.*;
 
 import java.io.IOException;
-import java.time.Duration;
-import java.util.Iterator;
-import java.util.List;
-import java.util.concurrent.CompletableFuture;
+import java.util.Map;
 
 public class Main {
   public static void main(String[] args) {
@@ -16,10 +13,17 @@ public static void main(String[] args) {
       natsURL = "nats://127.0.0.1:4222";
     }
 
-    try (Connection conn = Nats.connect(natsURL)) {
-      JetStreamManagement jsm = conn.jetStreamManagement();
+    try (Connection nc = Nats.connect(natsURL)) {
+      JetStreamManagement jsm = nc.jetStreamManagement();
       JetStream js = jsm.jetStream();
 
+      // Delete the stream, so we always have a fresh start for the example
+      // don't care if this, errors in this example, it will if the stream exists.
+      try {
+        jsm.deleteStream("subjects");
+      }
+      catch (Exception ignore) {}
+
       // Create a stream with a few subjects
       jsm.addStream(StreamConfiguration.builder()
           .name("subjects")
@@ -28,7 +32,7 @@ public static void main(String[] args) {
 
       // ### GetStreamInfo with StreamInfoOptions
       // Get the subjects via the getStreamInfo call.
-      // Since this is "state" a subject is not in the state unless
+      // Since this is "state" there are no subjects in the state unless
       // there are messages in the subject.
       StreamInfo si = jsm.getStreamInfo("subjects", StreamInfoOptions.allSubjects());
       StreamState state = si.getStreamState();
@@ -41,22 +45,26 @@ public static void main(String[] args) {
       state = si.getStreamState();
       System.out.println("After publishing a message to a subject, it appears in state:");
       for (Subject s : state.getSubjects()) {
-        System.out.println("  "  + s);
+        System.out.println("  subject '" + s.getName() + "' has " + s.getCount() + " message(s)");
       }
 
       // Publish some more messages, this time against wildcard subjects
-      js.publish("greater.A", null);
-      js.publish("greater.A.B", null);
-      js.publish("greater.A.B.C", null);
-      js.publish("greater.B.B.B", null);
-      js.publish("star.1", null);
-      js.publish("star.2", null);
+      js.publish("greater.A", "gtA-1".getBytes());
+      js.publish("greater.A", "gtA-2".getBytes());
+      js.publish("greater.A.B", "gtAB-1".getBytes());
+      js.publish("greater.A.B", "gtAB-2".getBytes());
+      js.publish("greater.A.B.C", "gtABC".getBytes());
+      js.publish("greater.B.B.B", "gtBBB".getBytes());
+      js.publish("star.1", "star1-1".getBytes());
+      js.publish("star.1", "star1-2".getBytes());
+      js.publish("star.2", "star2".getBytes());
 
+      // Get all subjects, but get the subjects as a map, via getSubjectMap
       si = jsm.getStreamInfo("subjects", StreamInfoOptions.allSubjects());
       state = si.getStreamState();
       System.out.println("Wildcard subjects show the actual subject, not the template.");
-      for (Subject s : state.getSubjects()) {
-        System.out.println("  "  + s);
+      for (Map.Entry<String, Long> entry : state.getSubjectMap().entrySet()) {
+        System.out.println("  subject '" + entry.getKey() + "' has " + entry.getValue() + " message(s)");
       }
 
       // ### Subject Filtering
@@ -65,21 +73,17 @@ public static void main(String[] args) {
       state = si.getStreamState();
       System.out.println("Filtering the subject returns only matching entries ['greater.>']");
       for (Subject s : state.getSubjects()) {
-        System.out.println("  "  + s);
+        System.out.println("  subject '" + s.getName() + "' has " + s.getCount() + " message(s)");
       }
 
       si = jsm.getStreamInfo("subjects", StreamInfoOptions.filterSubjects("greater.A.>"));
       state = si.getStreamState();
       System.out.println("Filtering the subject returns only matching entries ['greater.A.>']");
       for (Subject s : state.getSubjects()) {
-        System.out.println("  "  + s);
+        System.out.println("  subject '" + s.getName() + "' has " + s.getCount() + " message(s)");
       }
-    }
-    catch (JetStreamApiException | IOException | InterruptedException e) {
-      // * JetStreamApiException: the stream or consumer did not exist
-      // * IOException: problem making the connection
-      // * InterruptedException: thread interruption in the body of the example
-      System.out.println(e);
+    } catch (InterruptedException | IOException | JetStreamApiException e) {
+      e.printStackTrace();
     }
   }
 }