import java.util.Random; abstract class CommonState implements StateLessStateMachine.MachineState { protected void say() { System.out.println(" # " + this.getClass().getName()); } } class StartState extends CommonState { public StateLessStateMachine.State process() { say(); System.out.println(" GO!"); return StateLessStateMachine.State.TRY; } } class TryState extends CommonState { public StateLessStateMachine.State process() { StateLessStateMachine.State nextState = null; say(); int i = (new Random()).nextInt(6); switch (i) { case 1: System.out.println(" -> Success"); nextState = StateLessStateMachine.State.SUCCESS; break; default: System.out.println(" -> Failure"); nextState = StateLessStateMachine.State.FAILURE; break; } return nextState; } } class FailureState extends CommonState { public StateLessStateMachine.State process() { say(); System.out.println(" -> Retry"); return StateLessStateMachine.State.TRY; } } class SuccessState extends CommonState { public StateLessStateMachine.State process() { say(); System.out.println(" -> well done"); return StateLessStateMachine.State.STOP; } } class StateLessStateMachine { public enum State { STOP(-1), START(0), TRY(1), SUCCESS(2), FAILURE(3); public int i; State(int i) { this.i = i; } } interface MachineState { public State process(); } private MachineState[] states = { new StartState(), new TryState(), new SuccessState(), new FailureState() }; public State process(State currentState) { if (currentState == State.STOP) return currentState; return states[currentState.i].process(); } } public class StateLessStateMachineTest { public static void main(String [] args ) { System.out.println(StateLessStateMachineTest.class.getName()); StateLessStateMachine stm = new StateLessStateMachine(); StateLessStateMachine.State st = StateLessStateMachine.State.START; do { st = stm.process(st); } while (st != StateLessStateMachine.State.STOP); } }