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设计模式--组合模式
组合模式原理
餐 厅菜单聚类结构现状
添加餐后甜点子菜单
困难：数据结构？怎么遍历?
思考
餐厅菜单新需求导致的遍历困难
结构抽象
需要用树形结构，节点是菜单或子菜单，叶子是菜单项
需要能够在各个菜单项之间游走，遍历
要能够有弹性的在菜单项之间游走
组合模式的原理和设计方案
组合模式：将对象聚合成树形结构来表现“整体/部分”的层次结构。
组合模式能让客户以一致的方式来处理个别对象以及对象组合。
也就是我们可以忽略对象组合与个体对象之间的差别
组合模式示例代码讲解
示例项目类图结构
ComposeIterator
import java.util.Iterator;
import java.util.Stack;
public class ComposeIterator implements Iterator {
private Stack<Iterator> stack = new Stack<Iterator>(); //为了更好的遍历
public ComposeIterator(Iterator iterator) {
stack.push(iterator);
}
@Override
public boolean hasNext() {
// TODO Auto-generated method stub
if (stack.empty()) {
return false;
}
Iterator iterator = stack.peek();
if (!iterator.hasNext()) {
stack.pop();
return hasNext();
} else {
return true;
}
}
@Override
public Object next() {
// TODO Auto-generated method stub
if (hasNext()) {
Iterator iterator = stack.peek();
MenuComponent mMenuComponent = (MenuComponent) iterator.next();
stack.push(mMenuComponent.getIterator()); //专门再设计这一操作，能够访问它当前的下一层菜单项
return mMenuComponent;
}
return null;
}
@Override
public void remove() {
// TODO Auto-generated method stub
}
}
这里还设计了一个空的迭代器，意思是这里的菜单是空的
NullIterator
import java.util.Iterator;
public class NullIterator implements Iterator{
@Override
public boolean hasNext() {
// TODO Auto-generated method stub
return false;
}
@Override
public Object next() {
// TODO Auto-generated method stub
return null;
}
@Override
public void remove() {
// TODO Auto-generated method stub
}
}
MenuComponent
import java.util.Iterator;
public abstract class MenuComponent {
public String getName() {
return "";
}
public String getDescription() {
return "";
}
public float getPrice() {
return 0;
}
public boolean isVegetable() {
return false;
}
public abstract void print();
public Iterator getIterator() {
return new NullIterator();
}
}MenuItem
public class MenuItem extends MenuComponent{
private String name,description;
private boolean vegetable;
private float price;
public MenuItem(String name,String description,boolean vegetable,float price)
{
this.name=name;
this.description=description;
this.vegetable=vegetable;
this.price=price;
}
@Override
public String getName()
{
return name;
}
@Override
public String getDescription()
{
return description;
}
@Override
public float getPrice()
{
return price;
}
@Override
public boolean isVegetable()
{
return vegetable;
}
@Override
public void print() {
// TODO Auto-generated method stub
System.out.println(getName() + "***" + getPrice() + "***"
+ getDescription());
}
}
SubMenu
import java.util.ArrayList;
import java.util.Iterator;
public class SubMenu extends MenuComponent {
private ArrayList<MenuComponent> menuItems;
public SubMenu() {
menuItems = new ArrayList<MenuComponent>();
addItem("Apple Cookie", "Apple&candy&Cookie", true, 1.99f);
addItem("Banana Cookie", "Banana&candy&Cookie", false, 1.59f);
addItem("Orange Cookie", "Orange&Cookie", true, 1.29f);
}
private void addItem(String name, String description, boolean vegetable,
float price) {
MenuItem menuItem = new MenuItem(name, description, vegetable, price);
menuItems.add(menuItem);
}
public Iterator getIterator() {
return new ComposeIterator(menuItems.iterator());
}
@Override
public void print() {
// TODO Auto-generated method stub
System.out.println("****This is SubMenu****");
};
// 其他功能代码
}
DinerMenu
public class DinerMenu extends MenuComponent {
private final static int Max_Items = 5;
private int numberOfItems = 0;
private MenuComponent[] menuItems;
public DinerMenu() {
menuItems = new MenuComponent[Max_Items];
addItem("vegetable Blt", "bacon&lettuce&tomato&cabbage", true, 3.58f);
addItem("Blt", "bacon&lettuce&tomato", false, 3.00f);
addItem("bean soup", "bean&potato salad", true, 3.28f);
addItem("hotdog", "onions&cheese&bread", false, 3.05f);
addSubMenu(new SubMenu());
}
private void addItem(String name, String description, boolean vegetable,
float price) {
MenuItem menuItem = new MenuItem(name, description, vegetable, price);
if (numberOfItems >= Max_Items) {
System.err.println("sorry,menu is full!can not add another item");
} else {
menuItems[numberOfItems] = menuItem;
numberOfItems++;
}
}
private void addSubMenu(MenuComponent mMenuComponent) {
if (numberOfItems >= Max_Items) {
System.err.println("sorry,menu is full!can not add another item");
} else {
menuItems[numberOfItems] = mMenuComponent;
numberOfItems++;
}
}
public Iterator getIterator() {
return new ComposeIterator(new DinerIterator());
}
class DinerIterator implements Iterator {
private int position;
public DinerIterator() {
position = 0;
}
@Override
public boolean hasNext() {
// TODO Auto-generated method stub
if (position < numberOfItems) {
return true;
}
return false;
}
@Override
public Object next() {
// TODO Auto-generated method stub
MenuComponent menuItem = menuItems[position];
position++;
return menuItem;
}
@Override
public void remove() {
// TODO Auto-generated method stub
}
}
@Override
public void print() {
// TODO Auto-generated method stub
System.out.println("****This is DinerMenu****");
};
}
CakeHouseMenu
import java.util.ArrayList;
import java.util.Iterator;
public class CakeHouseMenu extends MenuComponent {
private ArrayList<MenuComponent> menuItems;
public CakeHouseMenu() {
menuItems = new ArrayList<MenuComponent>();
addItem("KFC Cake Breakfast", "boiled eggs&toast&cabbage", true, 3.99f);
addItem("MDL Cake Breakfast", "fried eggs&toast", false, 3.59f);
addItem("Stawberry Cake", "fresh stawberry", true, 3.29f);
addItem("Regular Cake Breakfast", "toast&sausage", true, 2.59f);
}
private void addItem(String name, String description, boolean vegetable,
float price) {
MenuItem menuItem = new MenuItem(name, description, vegetable, price);
menuItems.add(menuItem);
}
public Iterator getIterator() {
return new ComposeIterator(menuItems.iterator());
}
@Override
public void print() {
// TODO Auto-generated method stub
System.out.println("****This is CakeHouseMenu****");
};
// 其他功能代码
}
Waitress
import java.util.ArrayList;
import java.util.Iterator;
public class Waitress {
private ArrayList<MenuComponent> iterators = new ArrayList<MenuComponent>();
public Waitress() {
}
public void addComponent(MenuComponent mMenuComponent) {
iterators.add(mMenuComponent);
}
public void printMenu() {
Iterator iterator;
MenuComponent menuItem;
for (int i = 0, len = iterators.size(); i < len; i++) {
iterators.get(i).print();
iterator = iterators.get(i).getIterator();
while (iterator.hasNext()) {
menuItem = (MenuComponent) iterator.next();
menuItem.print();
}
}
}
public void printBreakfastMenu() {
}
public void printLunchMenu() {
}
public void printVegetableMenu() {
Iterator iterator;
MenuComponent menuItem;
for (int i = 0, len = iterators.size(); i < len; i++) {
iterators.get(i).print();
iterator = iterators.get(i).getIterator();
while (iterator.hasNext()) {
menuItem = (MenuComponent) iterator.next();
if (menuItem.isVegetable()) {
menuItem.print();
}
}
}
}
}
MainTest
public class MainTest {
public static void main(String[] args) {
Waitress mWaitress = new Waitress();
CakeHouseMenu mCakeHouseMenu = new CakeHouseMenu();
DinerMenu mDinerMenu = new DinerMenu();
mWaitress.addComponent(mCakeHouseMenu);
mWaitress.addComponent(mDinerMenu);
mWaitress.printVegetableMenu();;
}
}