Menu : parent and child menu, collapsing the child under the parent menu

Menu.java

package menu.test;

import java.io.Serializable;
import java.util.List;

public class Menu implements Serializable {
	private Long id;
	private Long parentid;
	private String name;
	private List<Menu> childMenu;

	/**
	 * @return the id
	 */
	public Long getId() {
		return id;
	}

	/**
	 * @param id
	 *            the id to set
	 */
	public void setId(Long id) {
		this.id = id;
	}

	/**
	 * @return the parentid
	 */
	public Long getParentid() {
		return parentid;
	}

	/**
	 * @param parentid
	 *            the parentid to set
	 */
	public void setParentid(Long parentid) {
		this.parentid = parentid;
	}

	/**
	 * @return the name
	 */
	public String getName() {
		return name;
	}

	/**
	 * @param name
	 *            the name to set
	 */
	public void setName(String name) {
		this.name = name;
	}

	/**
	 * @return the childMenu
	 */
	public List<Menu> getChildMenu() {
		return childMenu;
	}

	/**
	 * @param childMenu
	 *            the childMenu to set
	 */
	public void setChildMenu(List<Menu> childMenu) {
		this.childMenu = childMenu;
	}

}

MenuService.java

package menu.test;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MenuService {
	public static void main(String[] args) {

		List<Menu> Listmenu = (List<Menu>) getMenu();
		System.out.println("UnOrdered Menu : ");
		for (Menu m : Listmenu) {
			System.out.println(m.getName());
		}

		Menu myMenu = new Menu();
		Map<Long, Menu> parentMenu = new HashMap<>();

		for (Menu menuOri : Listmenu) {
			populateMenu(menuOri, myMenu, parentMenu);
		}

		System.out.println("Ordered Menu : ");
		showPopulatedMenu(parentMenu);

	}

	private static void populateMenu(Menu menuOri, Menu myMenu, Map<Long, Menu> parentMenu) {
		if (menuOri.getParentid() == null) {
			// check if parent has exist in map, if exist dont put it again
			if (parentMenu.get(menuOri.getId()) == null) {
				// get parent
				myMenu = new Menu();
				myMenu.setId(menuOri.getId());
				myMenu.setName(menuOri.getName());
				parentMenu.put(myMenu.getId(), myMenu);
			}

		} else {
			// get child
			getChild(menuOri, myMenu, parentMenu);
		}

		// populateMenu(menuOri, myMenu, parentMenu);

	}

	private static void getChild(Menu menuOri, Menu myMenu, Map<Long, Menu> parentMenu) {
		// check if parent menu is exist in map
		if (parentMenu.get(menuOri.getParentid()) != null) {
			Menu childMenu = new Menu();
			// get its parent
			Menu parentMenuTemp = parentMenu.get(menuOri.getParentid());

			// if childMenu doesnt exist
			if (parentMenuTemp.getChildMenu() == null) {
				List<Menu> childMenuList = new ArrayList<>();
				// set up the child
				childMenu.setId(menuOri.getId());
				childMenu.setName(menuOri.getName());
				childMenu.setParentid(menuOri.getParentid());

				childMenuList.add(childMenu);
				// insert to its parent
				parentMenuTemp.setChildMenu(childMenuList);
			} else {

				// if there is/are another childMenu does exist
				List<Menu> childMenuList = parentMenuTemp.getChildMenu();
				// set up the child
				childMenu.setId(menuOri.getId());
				childMenu.setName(menuOri.getName());
				childMenu.setParentid(menuOri.getParentid());

				childMenuList.add(childMenu);
				// insert to its parent
				parentMenuTemp.setChildMenu(childMenuList);
			}
			// put it again the parent with new added child
			parentMenu.put(parentMenuTemp.getId(), parentMenuTemp);
		}

	}

	private static void showPopulatedMenu(Map<Long, Menu> parentMenu) {
		for (Map.Entry<Long, Menu> parentMap : parentMenu.entrySet()) {
			Menu parent = parentMap.getValue();
			System.out.println("(+) " + parent.getName());
			if (parent.getChildMenu() != null) {
				for (Menu child : parent.getChildMenu()) {
					System.out.println("--- " + child.getName());
				}
			}
		}

	}

	private static List<Menu> getMenu() {
		List<Menu> list = new ArrayList<>();

		Menu m = new Menu();
		m.setId(1l);
		m.setName("Elektronik");
		list.add(m);

		m = new Menu();
		m.setId(2l);
		m.setName("kulkas");
		m.setParentid(1l);
		list.add(m);

		m = new Menu();
		m.setId(3l);
		m.setName("rice cooker");
		m.setParentid(1l);
		list.add(m);

		m = new Menu();
		m.setId(4l);
		m.setName("Pakaian");
		list.add(m);

		m = new Menu();
		m.setId(5l);
		m.setName("T-shirt");
		m.setParentid(4l);
		list.add(m);

		m = new Menu();
		m.setId(6l);
		m.setName("Celana");
		m.setParentid(4l);
		list.add(m);

		m = new Menu();
		m.setId(7l);
		m.setName("Gadget");
		list.add(m);

		m = new Menu();
		m.setId(8l);
		m.setName("samsung");
		m.setParentid(7l);
		list.add(m);

		m = new Menu();
		m.setId(8l);
		m.setName("apple");
		m.setParentid(7l);
		list.add(m);

		m = new Menu();
		m.setId(9l);
		m.setName("Dvd player");
		m.setParentid(1l);
		list.add(m);

		m = new Menu();
		m.setId(8l);
		m.setName("htc");
		m.setParentid(7l);
		list.add(m);

		m = new Menu();
		m.setId(6l);
		m.setName("jaket");
		m.setParentid(4l);
		list.add(m);

		return list;

	}

}

menu parent and child
membuat menu, yang terdapat child and parent menu