Embedded Files
Java is object oriented so its natural to model a state as an object. Consider (and run) the following program (from here) that models a vending machine; it's a complex program that will take some time to understand; try running it in the debugger:
import java.util.*;
public class StateMachine {
private enum State {
// each state and its transitions (actions)
Ready(true, "Deposit", "Quit"),
Waiting(true, "Select", "Refund"),
Dispensing(true, "Remove"),
Refunding(false, "Refunding"),
Exiting(false, "Quiting");
State(boolean is_explicit, String... in) {
inputs = Arrays.asList(in);
explicit = is_explicit;
}
State nextState(String input, State current) {
if (inputs.contains(input)) {
return map.getOrDefault(input, current);
}
return current;
}
final List<String> inputs;
final static Map<String, State> map = new HashMap<>();
final boolean explicit;
// Map contains transitions, next state
static {
map.put("Deposit", State.Waiting);
map.put("Quit", State.Exiting);
map.put("Select", State.Dispensing);
map.put("Refund", State.Refunding);
map.put("Remove", State.Ready);
map.put("Refunding", State.Ready);
}
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
State state = State.Ready;
while (state != State.Exiting) {
System.out.println(state.inputs);
if (state.explicit){
System.out.print("> ");
state = state.nextState(sc.nextLine().trim(), state);
} else {
state = state.nextState(state.inputs.get(0), state);
}
}
sc.close();
}
}
Read more about implementing state machines in Java in these advanced tutorials here and here
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