637: Default generator should not be static

Change-Id: Ib1f90d5a25f1c5db32ff9c838cfbeb35aac5d671
(cherry picked from commit 59e9455)

Author: janssk1

src/main/java/com/rabbitmq/client/IncrementingCorrelationIdGenerator.java

@@ -15,4 +15,8 @@ public IncrementingCorrelationIdGenerator(String _prefix) {
     public String get() {
         return _prefix + _correlationId++;
     }
+
+    public int getCorrelationId() {
+        return _correlationId;
+    }
 }

src/main/java/com/rabbitmq/client/RpcClient.java

@@ -481,6 +481,19 @@ public Map<String, BlockingCell<Object>> getContinuationMap() {
         return _continuationMap;
     }
 
+    /**
+     * Retrieve the correlation id.
+     * @return the most recently used correlation id
+     * @deprecated Only works for {@link IncrementingCorrelationIdGenerator}
+     */
+    public int getCorrelationId() {
+        if (_correlationIdGenerator instanceof IncrementingCorrelationIdGenerator) {
+            return ((IncrementingCorrelationIdGenerator) _correlationIdGenerator).getCorrelationId();
+        } else {
+            throw new UnsupportedOperationException();
+        }
+    }
+
     /**
      * Retrieve the consumer.
      * @return an interface to the client's consumer object