Tree Encoding

Tree.java

package co.fwoar.java.tree;

import java.util.ArrayDeque;
import java.util.Deque;

public class Main {
    static class Tree {
        public int val;
        public Tree left;
        public Tree right;

        public Tree(int val, Tree left, Tree right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }

    static Tree Tree(int val, Tree left, Tree right) {
        return new Tree(val, left, right);
    }

    static class Codec {
        public String encode(Tree tree) {
            if (tree == null) return "n";
            var lString = encode(tree.left);
            var rString = encode(tree.right);
            return String.format("%s %s %d t", lString, rString, tree.val);
        }

        enum Type {
            TREE,
            NUM,
            NULL
        }

        static class Wrapper {
            Type type;
            Tree t;
            int i;

            public Wrapper(Tree t) {
                this.type = Type.TREE;
                this.t = t;
            }

            public Wrapper(int i) {
                this.type = Type.NUM;
                this.i = i;
            }

            public Wrapper() {
                this.type = Type.NULL;
            }

            @Override
            public String toString() {
                return "Wrapper{" +
                        "type=" + type +
                        ", t=" + t +
                        ", i=" + i +
                        '}';
            }
        }

        public Tree decode(String[] tokens) {
            Deque<Wrapper> stack = new ArrayDeque<>();
            for (var token : tokens) {
                if (token.equals("n")) {
                    stack.push(new Wrapper());
                } else if (token.equals("t")) {
                    var v = stack.pop();
                    var r = stack.pop();
                    var l = stack.pop();
                    stack.push(new Wrapper(Tree(v.i, l.t, r.t)));
                } else {
                    var val = Integer.parseInt(token, 10);
                    stack.push(new Wrapper(val));
                }
            }
            return stack.pop().t;
        }

        public Tree decode(String string) {
            var tokens = string.split(" ");
            return decode(tokens);
        }
    }

    public static void main(String[] args) {
        var t = Tree(1, Tree(2, null, null), Tree(3, null, Tree(4, null, null)));
        var c = new Codec();
        System.out.println(c.encode(t));
        System.out.println(c.encode(c.decode(c.encode(t))));
    }
}