An example for RoseTree in Java 8

RoseTree.java

import java.util.List;
import java.util.Arrays;

public class RoseTree<T> {
	private final T value;
	private final List<RoseTree<T>> children;

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

	public int count() {
		return 1 + children.stream().mapToInt(RoseTree::count).sum();
	}

	public int countLeaves() {
		if (children.isEmpty()) return 1;
		return children.stream().mapToInt(RoseTree::countLeaves).sum();
	}

	public int height() {
		return 1 + children.stream().mapToInt(RoseTree::height).max().orElse(0);
	}

	@SafeVarargs
	private static <T> RoseTree<T> rose(T value, RoseTree<T>... children) {
		return new RoseTree<>(value, Arrays.asList(children));
	}

	public static void main(String[] args) {
		RoseTree<Integer> t = rose(1, rose(2), rose(3));
		System.out.println(t.countLeaves());
		System.out.println(t.count());
		System.out.println(t.height());
	}
}