[Java] Fix incorrect visibility and some minor cleanup (#3112)

clients/java/signalr/src/main/java/com/microsoft/signalr/CallbackMap.java

@@ -7,7 +7,7 @@ import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;
 
 class CallbackMap {
-    private Map<String, List<InvocationHandler>> handlers = new ConcurrentHashMap<>();
+    private final Map<String, List<InvocationHandler>> handlers = new ConcurrentHashMap<>();
 
     public InvocationHandler put(String target, ActionBase action, Class<?>... classes) {
         InvocationHandler handler = new InvocationHandler(action, classes);

clients/java/signalr/src/main/java/com/microsoft/signalr/DefaultHttpClient.java

@@ -22,8 +22,8 @@ import okhttp3.RequestBody;
 import okhttp3.Response;
 import okhttp3.ResponseBody;
 
-class DefaultHttpClient extends HttpClient {
-    private OkHttpClient client;
+final class DefaultHttpClient extends HttpClient {
+    private final OkHttpClient client;
     private Logger logger;
 
     public DefaultHttpClient(Logger logger) {

clients/java/signalr/src/main/java/com/microsoft/signalr/HandshakeProtocol.java

@@ -5,7 +5,7 @@ package com.microsoft.signalr;
 
 import com.google.gson.Gson;
 
-class HandshakeProtocol {
+final class HandshakeProtocol {
     private static final Gson gson = new Gson();
     private static final String RECORD_SEPARATOR = "\u001e";
 

clients/java/signalr/src/main/java/com/microsoft/signalr/HttpHubConnectionBuilder.java

@@ -8,7 +8,7 @@ import java.time.Duration;
 import io.reactivex.Single;
 
 public class HttpHubConnectionBuilder {
-    private String url;
+    private final String url;
     private Transport transport;
     private Logger logger;
     private HttpClient httpClient;
@@ -56,7 +56,7 @@ public class HttpHubConnectionBuilder {
         return this;
     }
 
-    HttpHubConnectionBuilder withHandshakeResponseTimeout(Duration timeout) {
+    public HttpHubConnectionBuilder withHandshakeResponseTimeout(Duration timeout) {
         this.handshakeResponseTimeout = timeout;
         return this;
     }

clients/java/signalr/src/main/java/com/microsoft/signalr/HubConnection.java

@@ -24,28 +24,28 @@ import io.reactivex.Single;
 
 public class HubConnection {
     private static final String RECORD_SEPARATOR = "\u001e";
-    private static List<Class<?>> emptyArray = new ArrayList<>();
-    private static int MAX_NEGOTIATE_ATTEMPTS = 100;
+    private static final List<Class<?>> emptyArray = new ArrayList<>();
+    private static final int MAX_NEGOTIATE_ATTEMPTS = 100;
 
-    private String baseUrl;
+    private final String baseUrl;
     private Transport transport;
     private OnReceiveCallBack callback;
-    private CallbackMap handlers = new CallbackMap();
+    private final CallbackMap handlers = new CallbackMap();
     private HubProtocol protocol;
     private Boolean handshakeReceived = false;
     private HubConnectionState hubConnectionState = HubConnectionState.DISCONNECTED;
-    private Lock hubConnectionStateLock = new ReentrantLock();
+    private final Lock hubConnectionStateLock = new ReentrantLock();
     private Logger logger;
     private List<Consumer<Exception>> onClosedCallbackList;
-    private boolean skipNegotiate;
+    private final boolean skipNegotiate;
     private Single<String> accessTokenProvider;
-    private Map<String, String> headers = new HashMap<>();
+    private final Map<String, String> headers = new HashMap<>();
     private ConnectionState connectionState = null;
-    private HttpClient httpClient;
+    private final HttpClient httpClient;
     private String stopError;
     private Timer pingTimer = null;
-    private AtomicLong nextServerTimeout = new AtomicLong();
-    private AtomicLong nextPingActivation = new AtomicLong();
+    private final AtomicLong nextServerTimeout = new AtomicLong();
+    private final AtomicLong nextPingActivation = new AtomicLong();
     private Duration keepAliveInterval = Duration.ofSeconds(15);
     private Duration serverTimeout = Duration.ofSeconds(30);
     private Duration tickRate = Duration.ofSeconds(1);

clients/java/signalr/src/main/java/com/microsoft/signalr/HubConnectionBuilder.java

@@ -4,12 +4,11 @@
 package com.microsoft.signalr;
 
 public abstract class HubConnectionBuilder {
-
     public static HttpHubConnectionBuilder create(String url) {
         if (url == null || url.isEmpty()) {
             throw new IllegalArgumentException("A valid url is required.");
         }
-     return new HttpHubConnectionBuilder(url);
+        return new HttpHubConnectionBuilder(url);
     }
 
     public abstract HubConnection build();

clients/java/signalr/src/main/java/com/microsoft/signalr/HubException.java

@@ -4,6 +4,8 @@
 package com.microsoft.signalr;
 
 public class HubException extends Exception {
+    private static final long serialVersionUID = -572019264269821519L;
+
     public HubException() {
     }
 

clients/java/signalr/src/main/java/com/microsoft/signalr/InvocationHandler.java

@@ -7,8 +7,8 @@ import java.util.Arrays;
 import java.util.List;
 
 class InvocationHandler {
-    private List<Class<?>> classes;
-    private ActionBase action;
+    private final List<Class<?>> classes;
+    private final ActionBase action;
 
     InvocationHandler(ActionBase action, Class<?>... classes) {
         this.action = action;

clients/java/signalr/src/main/java/com/microsoft/signalr/InvocationRequest.java

@@ -6,9 +6,9 @@ package com.microsoft.signalr;
 import java.util.concurrent.CompletableFuture;
 
 class InvocationRequest {
-    private Class<?> returnType;
-    private CompletableFuture<Object> pendingCall = new CompletableFuture<>();
-    private String invocationId;
+    private final Class<?> returnType;
+    private final CompletableFuture<Object> pendingCall = new CompletableFuture<>();
+    private final String invocationId;
 
     InvocationRequest(Class<?> returnType, String invocationId) {
         this.returnType = returnType;

clients/java/signalr/src/main/java/com/microsoft/signalr/PingMessage.java

@@ -5,7 +5,7 @@ package com.microsoft.signalr;
 
 class PingMessage extends HubMessage
 {
-    int type = HubMessageType.PING.value;
+    private final int type = HubMessageType.PING.value;
 
     private static PingMessage instance = new PingMessage();
 

clients/java/signalr/src/main/java/com/microsoft/signalr/StreamInvocationMessage.java

@@ -4,8 +4,7 @@
 package com.microsoft.signalr;
 
 class StreamInvocationMessage extends InvocationMessage {
-
-    int type = HubMessageType.STREAM_INVOCATION.value;
+    private final int type = HubMessageType.STREAM_INVOCATION.value;
 
     public StreamInvocationMessage(String invocationId, String target, Object[] arguments) {
         super(invocationId, target, arguments);

clients/java/signalr/src/main/java/com/microsoft/signalr/Subscription.java

@@ -6,9 +6,9 @@ package com.microsoft.signalr;
 import java.util.List;
 
 public class Subscription {
-    private CallbackMap handlers;
-    private InvocationHandler handler;
-    private String target;
+    private final CallbackMap handlers;
+    private final InvocationHandler handler;
+    private final String target;
 
     public Subscription(CallbackMap handlers, InvocationHandler handler, String target) {
         this.handlers = handlers;

clients/java/signalr/src/main/java/com/microsoft/signalr/TransferFormat.java

@@ -3,7 +3,7 @@
 
 package com.microsoft.signalr;
 
-public enum TransferFormat {
+enum TransferFormat {
     TEXT,
     BINARY
 }

clients/java/signalr/src/main/java/com/microsoft/signalr/WebSocketTransport.java

@@ -13,8 +13,8 @@ class WebSocketTransport implements Transport {
     private Consumer<String> onClose;
     private String url;
     private Logger logger;
-    private HttpClient client;
-    private Map<String, String> headers;
+    private final HttpClient client;
+    private final Map<String, String> headers;
 
     private static final String HTTP = "http";
     private static final String HTTPS = "https";