Implementation of Turing Machine (use JShell to run)

turing.java

// https://docs.oracle.com/javase/8/docs/api/java/util/Stack.html

enum Head { LEFT, RIGHT, NONE }

class Transition { // data container only
    final String from, to;
    final Character read, write;
    final Head move;
    Transition(String from, Character read, Character write, Head move, String to) {
        this.from = from;
        this.read = read;
        this.write = write;
        this.move = move;
        this.to = to;
    }
    public String toString() {
        return from + "(" + read + "): " + write + ", " + move + " -> " + to; 
    }
}

class Machine {
    Collection<Transition> transitions = new ArrayList<>();
    Stack<Character> left = new Stack<>();
    Stack<Character> right = new Stack<>();
    Character empty = '.';
    String state;

    Machine(String left, String right) {
        for(Character c : left.toCharArray()) this.left.push(c);
        String thgir = new StringBuilder(right).reverse().toString();
        for(Character c : thgir.toCharArray()) this.right.push(c);
    }

    void move(Head move) {   
        switch (move) {
            case RIGHT:
                left.push(right.isEmpty() ? empty : right.pop());
                break;
            case LEFT:
                right.push(left.isEmpty() ? empty : left.pop());
                break;
            default: break;
        }
    }

    void add(Transition t) {
        if (t != null) transitions.add(t);
    }

    void action() {
        Character symbol = right.isEmpty() ? empty : right.pop();
        Transition t = find(state,symbol);
        right.push(t.write);
        move(t.move);
        state = t.to;
    }

    Transition find(String state, Character read) {
        for(Transition t : transitions)
            if (t.from == state && t.read == read) return t;
        return null;
    }

    void run() {
        while(!state.equals("HALT"))
            action();
    }

    public String toString() {
        Stack<Character> thgir = new Stack<>();
        return left + "<+>" + right;
    }
}

// example from https://de.wikipedia.org/wiki/Turingmaschine
Machine m = new Machine("","11000");
m.add(new Transition("s1",'1','0',Head.RIGHT,"s2"));
m.add(new Transition("s1",'0','0',Head.NONE,"HALT"));
m.add(new Transition("s2",'1','1',Head.RIGHT,"s2"));
m.add(new Transition("s2",'0','0',Head.RIGHT,"s3"));
m.add(new Transition("s3",'1','1',Head.RIGHT,"s3"));
m.add(new Transition("s3",'0','1',Head.LEFT,"s4"));
m.add(new Transition("s4",'1','1',Head.LEFT,"s4"));
m.add(new Transition("s4",'0','0',Head.LEFT,"s5"));
m.add(new Transition("s5",'1','1',Head.LEFT,"s5"));
m.add(new Transition("s5",'0','1',Head.RIGHT,"s1"));
m.state = "s1";