어제 보다 나은 오늘의 나

public class HierarchyNode {
    private final int data;
    private HierarchyNode child;
    private HierarchyNode sibling;

    public HierarchyNode(int data) {
        this(data, null, null);
    }

    private HierarchyNode(int data, HierarchyNode child, HierarchyNode sibling) {
        this.data = data;
        this.child = child;
        this.sibling = sibling;
    }

    public HierarchyNode appendToChild(int data) {
        if (child == null) {
            child = new HierarchyNode(data);
            return child;
        }
        return child.appendToSibling(data);
    }

    private HierarchyNode appendToSibling(int data) {
        if (sibling == null) {
            sibling = new HierarchyNode(data);
            return sibling;
        }
        return sibling.appendToSibling(data);
    }


    public int getData() {
        return data;
    }

    public HierarchyNode getChild() {
        return child;
    }

    public HierarchyNode getSibling() {
        return sibling;
    }

    public List<HierarchyNode> getChildren() {
        List<HierarchyNode> children = new ArrayList<>();
        if (child == null)
            return Collections.EMPTY_LIST;

        HierarchyNode tempChild = child;
        while (tempChild != null) {
            children.add(tempChild);
            tempChild = tempChild.getSibling();
        }
        return children;
    }

    public HierarchyNode findChild(int data) {
        Optional<HierarchyNode> first = getChildren().stream().filter(n -> data == n.getData()).findFirst();
        if (!first.isPresent())
            return null;
        return first.get();
    }
}

 public class HierarchyNodeTest {


    private HierarchyNode node;

    @Before
    public void setUp() throws Exception {
        node = new HierarchyNode(1);
        node.appendToChild(2);
        node.appendToChild(3);
        node.appendToChild(4);
    }

    @Test
    public void test_children() throws Exception {
        printChildren(node);

        int expectedData = 2;
        for (HierarchyNode each : node.getChildren()) {
            assertThat(each.getData(), is(expectedData++));
        }

    }

    private void printChildren(HierarchyNode node) {
        List<HierarchyNode> children = node.getChildren();
        System.out.println(node.getData());
        children.stream().map(n-> n.getData()).forEach(n -> System.out.println(String.format("ㄴ %d", n)));
    }

    @Test
    public void test_appendToChild() throws Exception {
        node.appendToChild(5);

        int expectedData = 2;
        HierarchyNode siblingOfChild = node.getChild();
        while(siblingOfChild != null) {
            assertThat(siblingOfChild.getData(), is(expectedData++));
            siblingOfChild = siblingOfChild.getSibling();
        }
    }


}

 public class HierarchyNodeMain {

    public static void main(String... arg) {

        HierarchyNode node = new HierarchyNode(1);
        HierarchyNode node2Of1 = node.appendToChild(2);
        node.appendToChild(3);
        node.appendToChild(4);

        node2Of1.appendToChild(5);
        node2Of1.appendToChild(6);
        HierarchyNode node7Of2 = node2Of1.appendToChild(7);
        node7Of2.appendToChild(10);
        node7Of2.appendToChild(11);
        node7Of2.appendToChild(12);

        HierarchyNode newNode = node;
        while ( newNode != null ) {
            printChildren(newNode);

            Scanner sc = new Scanner(System.in);
            System.out.println("다음 노드 선택 해주세요.(종료:q) : ");
            String input = sc.nextLine();
            if ("q".equals(input)) {
                newNode = null;
            } else {
                newNode = newNode.findChild(Integer.parseInt(input));
            }

            if (newNode == null) {
                System.out.println("종료되었습니다.");
            }
        }

    }

    private static void printChildren(HierarchyNode node) {
        List<HierarchyNode> children = node.getChildren();
        System.out.println(node.getData());
        children.stream().map(n-> n.getData()).forEach(n -> System.out.println(String.format("ㄴ %d", n)));
    }
}