How to execute a method asynchronously on same thread in Java?

Java 8 introduced CompletableFuture in java.util.concurrent.CompletableFuture, can be used to make a asynch call :

 CompletableFuture.runAsync(() -> { // method call or code to be asynch. }); 

Oh nice, this is a good example for Future<T>

A Future represents the result of an asynchronous computation. Methods are provided to check if the computation is complete, to wait for its completion, and to retrieve the result of the computation. If you would like to use a Future for the sake of cancellability but not provide a usable result, you can declare types of the form Future and return null as a result of the underlying task.
Source: JavaDoc

Here is a really simple working example to achieve what you are asking for

// Using Lambda Expression Future<Void> future = CompletableFuture.runAsync(() -> { // Simulate a long-running Job try { TimeUnit.SECONDS.sleep(1); } catch (InterruptedException e) { throw new IllegalStateException(e); } System.out.println("I'll run in a separate thread than the main thread."); }); // Start the future task without blocking main thread future.get() 

Under the hoods it's still another thread, just to clarify it