java组合模式

模式定义
组合模式允许你将对象组合成树形结构来表现“整体/部分”层次结构。组合能让客户以一致的方式处理个别对象以及对象组合

UML类图

例

package composite;

import java.util.Iterator;

/**
* Component
*
* @author chenhong
*
* */
public abstract class MenuComponent {

public void add(MenuComponent menuComponent) {
throw new UnsupportedOperationException();
}

public void remove(MenuComponent menuComponent) {
throw new UnsupportedOperationException();
}

public MenuComponent getChild(int i) {
throw new UnsupportedOperationException();
}

public String getName() {
throw new UnsupportedOperationException();
}

public String getDexcription() {
throw new UnsupportedOperationException();
}

public double getPrice() {
throw new UnsupportedOperationException();
}

public void print() {
throw new UnsupportedOperationException();
}

public Iterator iterator() {
throw new UnsupportedOperationException();
}
}

package composite;

/**
* leaf
*
* @author chenhong
*
* */
public class MenuItem extends MenuComponent {

String name;
String description;
double price;

public MenuItem(String name, String description, double price) {
this.name = name;
this.description = description;
this.price = price;
}

public String getName() {
return name;
}

public String getDescription() {
return description;
}

public double getPrice() {
return price;
}

public void print() {
System.out.print(" " + getName());
System.out.println("," + getPrice());
System.out.println("   ---" + getDescription());
}
}

package composite;

import java.util.ArrayList;
import java.util.Iterator;

/**
* Composite
*
* @author chenhong
* */
public class Menu extends MenuComponent {
ArrayList menuComponents = new ArrayList();
String name;
String description;

public Menu(String name, String description) {
this.name = name;
this.description = description;
}

public void add(MenuComponent menuComponent) {
menuComponents.add(menuComponent);
}

public void remove(MenuComponent menuComponent) {
menuComponents.remove(menuComponent);
}

public MenuComponent getChile(int i) {
return (MenuComponent) menuComponents.get(i);
}

public String getName() {
return name;
}

public String getDescription() {
return description;
}

public void print() {
System.out.print("\n" + getName());
System.out.println("," + getDescription());
System.out.println("-------------------");

Iterator iterator = menuComponents.iterator();
while (iterator.hasNext()) {
MenuComponent menuComponent = (MenuComponent) iterator.next();
menuComponent.print();
}

}

public Iterator iterator() {
return menuComponents.iterator();
}

}

package composite;

/**
* client
*
* @author chenhong
* */
public class Waitress {

MenuComponent allMenus;

public Waitress(MenuComponent allMenus) {
this.allMenus = allMenus;
}

public void printMenu() {
allMenus.print();
}
}

package composite;

public class MenuTestDrive {

public static void main(String args[]) {
MenuComponent pancakeHouseMenu = new Menu("早餐厅菜单", "Breakfast");
MenuComponent dinnerMenu = new Menu("晚餐厅菜单", "dinner");
MenuComponent cafeMenu = new Menu("咖啡厅菜单", "Dinner");
MenuComponent dessertMenu = new Menu("甜品菜单", "Dessert");

MenuComponent allMenus = new Menu("所有菜单", "All menus");
allMenus.add(pancakeHouseMenu);
allMenus.add(dinnerMenu);
allMenus.add(cafeMenu);

dinnerMenu.add(new MenuItem("鸡蛋炒饭", "鸡蛋＋饭", 3.89));
dinnerMenu.add(dessertMenu);

dessertMenu.add(new MenuItem("草莓派", "草莓＋面粉", 1.59));

/* 此处加入更多菜单 */

Waitress waitress = new Waitress(allMenus);
waitress.printMenu();
}
}

模式总结

1. 组合模式让我们能用树形方式创建对象的结构，树里面包含了组合以及个别的对象

2. 使用组合结构，我们能把相同的操作应用在组合和个别对象上。换句话说，在大多数情况下，我们可以忽略对象组合和个别对象之间的差别。