Use Lock interface to declare properties

Not ReentrantLock.

References #1119

src/main/java/com/rabbitmq/client/impl/AMQChannel.java

@@ -32,6 +32,7 @@
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.function.Supplier;
 
@@ -56,7 +57,7 @@ public abstract class AMQChannel extends ShutdownNotifierComponent {
      * so that clients can themselves use the channel to synchronize
      * on.
      */
-    protected final ReentrantLock _channelLock = new ReentrantLock();
+    protected final Lock _channelLock = new ReentrantLock();
     protected final Condition _channelLockCondition = _channelLock.newCondition();
 
     /** The connection this channel is associated with. */

src/main/java/com/rabbitmq/client/impl/AMQCommand.java

@@ -18,6 +18,7 @@
 import java.io.ByteArrayOutputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
+import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
 import com.rabbitmq.client.AMQP;
@@ -44,7 +45,7 @@ public class AMQCommand implements Command {
 
     /** The assembler for this command - synchronised on - contains all the state */
     private final CommandAssembler assembler;
-    private final ReentrantLock assemblerLock = new ReentrantLock();
+    private final Lock assemblerLock = new ReentrantLock();
 
     AMQCommand(int maxBodyLength) {
         this(null, null, null, maxBodyLength);

src/main/java/com/rabbitmq/client/impl/SocketFrameHandler.java

@@ -29,6 +29,7 @@
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Future;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
 /**
@@ -49,11 +50,11 @@ public class SocketFrameHandler implements FrameHandler {
 
     /** Socket's inputstream - data from the broker - synchronized on */
     private final DataInputStream _inputStream;
-    private final ReentrantLock _inputStreamLock = new ReentrantLock();
+    private final Lock _inputStreamLock = new ReentrantLock();
 
     /** Socket's outputstream - data to the broker - synchronized on */
     private final DataOutputStream _outputStream;
-    private final ReentrantLock _outputStreamLock = new ReentrantLock();
+    private final Lock _outputStreamLock = new ReentrantLock();
 
     private final int maxInboundMessageBodySize;