Simple Finite State Machine

Finite state machine implemented in Java language

Sample code and instructions

SimpleFSM fsm = new SimpleFSM() { (1)
      @Override
      public void onExit(Exception ex) { (2)
        System.out.println("THE END with error=" + ex);
        System.out.println("vals = " + Arrays.toString(  (int[]) this.get("val")) );
      }

    };


    int secs[] = new int[]{3, 0};
    Node n2 = fsm.addState("T1", () -> { (3)
      System.out.printf("First Node  pausa=%d secs\n", secs[0]);

      TimeUnit.SECONDS.sleep(secs[0]--);

    }).setTimeout(2000) (4)
      .setRetries(5); (4)

    fsm.addState(() -> { (3)
      System.out.println("no name");
      if (val[1]++ == 0) throw new Exception("I don´t like zeros!");
    }).setNextOnError("T1"); (5)


    fsm.addState("T3", () -> {
      System.out.println("Third Node");
      secs[0] = 7;
    }).setNext("T1"); (4)



    //Redirect the log output to the sys out
    //fsm.setLogStream(System.out); (6)
    fsm.print(); (7)
    fsm.start(); (8)
    //fsm.startInSameThread(); (9)

    // System.out.println("Must stop now!!");
    // fsm.mustStop();

How to use

1. Implement an object of the class SimpleFSM

2. If you want you can override the onExit method to be signalized when the FSM finishes

3. Add a state, you can pass a name or ommit it.

4. You can define the Timeout, number of retries and the next state to be executed on success

5. …​ or the next one to go in when something goes wrong

6. Define your log output

7. Print the nodes

8. Start the state machine on a separate thread

9. Start the state machine on the current thread

Bonus

The SimpleFSM is capable of store store variables, so like a hashmap, you are able to simply call: fsm.save(key, some_object ) and after the execution the value will be able to be got using fsm.get(key).

    final SimpleFSM fsm = new SimpleFSM() { (3)
      @Override
      public void onExit(Exception ex) {
        System.out.println("THE END with error=" + ex);
        System.out.println("vals = " + Arrays.toString(  (int[]) this.get("val")) ); (2)
      }
    };


    int val[] = new int[]{5, 0};
    Node n2 = fsm.addState("T1", () -> {
      System.out.printf("First Node  pausa=%d secs\n", val[0]);
      fsm.save("val", val ); (1)
      TimeUnit.SECONDS.sleep(val[0]--);
    }).setTimeout(2000)
      .setRetries(5);

1. Save the data using the fsm object (3)

2. Inside onExit we are in the fsm instance, so this points to the object itself

Finishing the FSM

If you need to close FSM using brute force, just use mustStop() It will finish all the pending threads, but will continue to call the ending method (onExit).

ENJOY !!!