Bump "Error Prone" to 2.0.15

and fix a few things :)

smack-debug-slf4j/src/main/java/org/jivesoftware/smackx/debugger/slf4j/SLF4JLoggingConnectionListener.java

@@ -40,22 +40,27 @@ class SLF4JLoggingConnectionListener implements ConnectionListener {
         logger.debug("({}) Connection authenticated as {}", connection.hashCode(), connection.getUser());
     }
 
+    @Override
     public void connectionClosed() {
         logger.debug("({}) Connection closed", connection.hashCode());
     }
 
+    @Override
     public void connectionClosedOnError(Exception e) {
         logger.debug("({}) Connection closed due to an exception: {}", connection.hashCode(), e);
     }
 
+    @Override
     public void reconnectionFailed(Exception e) {
         logger.debug("({}) Reconnection failed due to an exception: {}", connection.hashCode(), e);
     }
 
+    @Override
     public void reconnectionSuccessful() {
         logger.debug("({}) Connection reconnected", connection.hashCode());
     }
 
+    @Override
     public void reconnectingIn(int seconds) {
         logger.debug("({}) Connection will reconnect in {}", connection.hashCode(), seconds);
     }

smack-debug-slf4j/src/main/java/org/jivesoftware/smackx/debugger/slf4j/SLF4JLoggingPacketListener.java

@@ -31,6 +31,7 @@ class SLF4JLoggingPacketListener implements StanzaListener {
         this.prefix = Validate.notNull(prefix);
     }
 
+    @Override
     public void processStanza(Stanza packet) {
         if (SLF4JSmackDebugger.printInterpreted.get() && logger.isDebugEnabled()) {
             logger.debug("{}: PKT [{}] '{}'", prefix, packet.getClass().getName(), packet.toXML());

smack-debug-slf4j/src/main/java/org/jivesoftware/smackx/debugger/slf4j/SLF4JRawXmlListener.java

@@ -28,10 +28,12 @@ class SLF4JRawXmlListener implements ReaderListener, WriterListener {
         this.logger = Validate.notNull(logger);
     }
 
+    @Override
     public void read(String str) {
         logger.debug("{}: {}", SLF4JSmackDebugger.RECEIVED_TAG, str);
     }
 
+    @Override
     public void write(String str) {
         logger.debug("{}: {}", SLF4JSmackDebugger.SENT_TAG, str);
     }