Need help with Tree structure

[bagabont]

Hi there,
I have a task to

Create a program that:
-finds the shortest way which connects the root with a leaf in the Tree;
-finds the closest common parent of two given nodes A1 and A2 in the Tree;
-finds all nodes, which are simultaneously parents of nod A1 and children of nod A2 from the Tree;
-puts out on the screen a structure of the Tree,with the root on top.

I wonder how can i convert the printDFS function to display my Tree as in the picture below

FILE Tree.java

import java.util.ArrayList;

public class Tree<Type> {
	public static class TreeNode<Type> {
		private Type value;
		private boolean hasParent;
		private ArrayList<TreeNode<Type>> children;

		public TreeNode(Type value) {
			if (value == null) {
				throw new IllegalArgumentException("Cannot insert null value!");
			}
			this.value = value;
			this.children = new ArrayList<TreeNode<Type>>();
		}

		public Type getValue() {
			return this.value;
		}

		public void setValue(Type value) {
			this.value = value;
		}

		public void addChild(TreeNode<Type> child) {
			if (child == null) {
				throw new IllegalArgumentException("Cannot insert null value!");
			}
			if (child.hasParent) {
				throw new IllegalArgumentException(
						"The node already has a parent!");
			}
			child.hasParent = true;
			this.children.add(child);
		}

		public TreeNode<Type> getChild(int index) {
			return this.children.get(index);
		}

		public int getChildrenCount() {
			return this.children.size();
		}
	}

	private TreeNode<Type> root;

	public Tree(Type value) {
		if (value == null) {
			throw new IllegalArgumentException("Cannot insert null value!");
		}
		this.root = new TreeNode<Type>(value);
	}

	public Tree(Type value, Tree<Type>... children) {
		this(value);

		for (Tree<Type> child : children) {
			this.root.addChild(child.root);
		}
	}

	public TreeNode<Type> getRoot() {
		return this.root;
	}

	public ArrayList<TreeNode<Type>> getChildNodes() {
		if (this.root != null) {
			return this.root.children;
		}
		return new ArrayList<TreeNode<Type>>();
	}

	private void printDFS(TreeNode<Type> root, String spaces) {
		if (this.root == null) {
			return;
		}
		System.out.println(spaces + root.getValue());

		TreeNode<Type> child = null;
		for (int i = 0; i < root.getChildrenCount(); i++) {
			child = root.getChild(i);
			printDFS(child, spaces + "     ");
		}
	}

	public void printDFS() {
		this.printDFS(this.root, new String());
	}

}

FILE TreeExample.java

public class TreeExample {
  @SuppressWarnings("unchecked")
public static void main(String[] args) {
     Tree<Integer> tree =
       new Tree<Integer>(7,
    	    new Tree<Integer>(5,
    			new Tree<Integer>(5),
    			new Tree<Integer>(5)),
            new Tree<Integer>(19,
            		new Tree<Integer>(1),
            		new Tree<Integer>(12),
            		new Tree<Integer>(31)),
            new Tree<Integer>(21),
            new Tree<Integer>(14,
            		new Tree<Integer>(23),
            		new Tree<Integer>(6))
       );
     tree.printDFS();
  }
}

MY CURRENT DISPLAY OF THE TREE IS:

7
     5
          5
          5
     19
          1
          12
          31
     21
     14
          23
          6