Lightbend Activator

Akka FSM in Java with Lambdas

Akka FSM in Java with Lambdas

Akka Team
September 30, 2016
akka java java8 sample

Illustrating how to implement a finite state machine in actors.

How to get "Akka FSM in Java with Lambdas" on your computer

There are several ways to get this template.

Option 1: Choose akka-sample-fsm-java-lambda in the Lightbend Activator UI.

Already have Lightbend Activator (get it here)? Launch the UI then search for akka-sample-fsm-java-lambda in the list of templates.

Option 2: Download the akka-sample-fsm-java-lambda project as a zip archive

If you haven't installed Activator, you can get the code by downloading the template bundle for akka-sample-fsm-java-lambda.

  1. Download the Template Bundle for "Akka FSM in Java with Lambdas"
  2. Extract the downloaded zip file to your system
  3. The bundle includes a small bootstrap script that can start Activator. To start Lightbend Activator's UI:

    In your File Explorer, navigate into the directory that the template was extracted to, right-click on the file named "activator.bat", then select "Open", and if prompted with a warning, click to continue:

    Or from a command line:

     C:\Users\typesafe\akka-sample-fsm-java-lambda> activator ui 
    This will start Lightbend Activator and open this template in your browser.

Option 3: Create a akka-sample-fsm-java-lambda project from the command line

If you have Lightbend Activator, use its command line mode to create a new project from this template. Type activator new PROJECTNAME akka-sample-fsm-java-lambda on the command line.

Option 4: View the template source

The creator of this template maintains it at

Option 5: Preview the tutorial below

We've included the text of this template's tutorial below, but it may work better if you view it inside Activator on your computer. Activator tutorials are often designed to be interactive.

Preview the tutorial

Finite State Machine in Actors

This sample is an adaptation of Dining Hakkers. It illustrates how state and behavior can be managed within an Actor with two different approaches; using become and using the AbstractFSM class.

Dining Hakkers with Become


It illustrates how current behavior can be replaced with context.become. Note that no var members are used, instead the state is encoded in the current behavior and its parameters.

Go to the Run tab, and start the application main class sample.become.DiningHakkersOnBecome. In the log output you can see the actions of the Hakker actors.

Read more about become in the documentation.

Dining Hakkers with FSM


It illustrates how the states and transitions can be defined with the class.

Go to the Run tab, and start the application main class sample.fsm.DiningHakkersOnFsm. In the log output you can see the actions of the Hakker actors.

Read more about in the documentation.