SimpleStateMachine

SimpleStateMachine is a small util to build small state machines in Java

Download

The library is available on JCenter public repository

Gradle

implementation 'ru.romangr:simple-state-machine:0.0.3'

Maven

<dependency>
	<groupId>ru.romangr</groupId>
	<artifactId>simple-state-machine</artifactId>
	<version>0.0.3</version>
	<type>pom</type>
</dependency>

Usage

Declare states as a Java enum

enum ThreeStates {
  ONE,
  TWO,
  THREE
}

Declare events as a Java enum

enum TwoEvents {
  UP,
  DOWN
}

Build your state machine

    StateMachine<ThreeStates, TwoEvents> stateMachine = StateMachine.<ThreeStates, TwoEvents>builder()
        .withStates(ThreeStates.class)                                      // specify a list valid states
        .withEvents(TwoEvents.class)                                        // specify a list valid events
        .withInitialState(ThreeStates.ONE) // specify initial state         // specify an initial state
        .withTransition(ThreeStates.ONE, ThreeStates.TWO, TwoEvents.UP)     // declare some valid transitions
        .withTransition(ThreeStates.TWO, ThreeStates.ONE, TwoEvents.DOWN)
        .build();

Pass some event to the state machine

EventAcceptResult<ThreeStates> result = stateMachine.acceptEvent(TwoEvents.UP);

The result of this call consists of a new state and a result of passing the event. Possible results are declared in EventAcceptStatus enum

public enum EventAcceptStatus {
  SUCCESS,            // event has been successfully accepted and state machine have made a transition
  UNEXPECTED_EVENT    // event is not valid for the current state of the state machine, the state hasn't changed
}