Tree

import java.util.*;
import java.util.function.Consumer;

public class Tree<T> {
    private T value;
    private Tree<T>[] children;

    public Tree(T value, Tree<T>... children) {
        this.value = value;
        this.children = children;
    }

    // append output to builder
    public String print(int indent, StringBuilder builder) {
        String emptySpaces  = String.join("", Collections.nCopies(indent * 2, " "));

        builder.append(emptySpaces).append(this.value).append("\n");
        for (Tree<T> child : this.children) {
            child.print(indent+1, builder);
        }
        return builder.toString();
    }

    public void each(Consumer<T> consumer) {
        consumer.accept(this.value);
        for (Tree<T> child : this.children) {
            child.each(consumer);
        }
    }

    public Iterable<T> orderDFS() {
        List<T> result = new ArrayList<>();
        deepFirstTraversal(this, result);
        return result;
    }

    private void deepFirstTraversal(Tree<T> tree, List<T> result) {
        for (Tree<T> child : tree.children) {
            this.deepFirstTraversal(child,result);
        }
        result.add(tree.value);
    }

    public Iterable<T> orderBFS() {
        List<T> result = new ArrayList<>();
        Queue<Tree<T>> queue = new ArrayDeque<>();
        queue.offer(this);
        while (queue.size() > 0){
           Tree<T> current = queue.poll();
           result.add(current.value);

            for (Tree<T> child : current.children) {
                queue.offer(child);
            }
        }
        return result;
    }

}