Question: Is there is way to implement Async method call in java Other than thread and Executor ? If it is implementing by Executor will it introduce any delay ?

Answer: 
You could use the DynamicProxy (core java feature) to introduce a layer inbetween the caller and the callee. In the proxy you have the method call represented as an object. Return immediately and call the method in a separate thread. A question remains how to return values to the caller. Do you plan to have return values that you want to return later? This might be solved using a callback method.
You can pass in a class that implements your callback.

```
new A(instanceOfB);

someMethodOfA() {
    doSomething();
    instanceOfB.callback();
}

```