Java:
 .continueWithTask(
                new Continuation<Void, Task<Void>>() {
                    @Override
                    public Task<Void> then(Task<Void> task) throws Exception {
						synchronized (Class.this) {

						}
                    }
                }
            )

Kotlin:

.continueWithTask { task ->
   synchronized (this) {

   }
}