请求作为命令包装在一个对象下,并传递给调用器对象。 调用者对象查找可以处理此命令的适当对象,并将命令传递到执行命令的相应对象。
实现
创建了一个作为命令的接口- Order,同时也创建了一个Stock类作为请求。 有具体的命令类BuyStock和SellStock实现Order接口将做实际的命令处理。 将创建一个类Broker作为调用器对象。它可以接收和下订单,Broker对象使用命令模式来标识哪个对象,并根据命令类型执行哪个命令。
代码
package com.test;
import java.util.ArrayList;
import java.util.List;
//第1步,创建一个命令接口
interface Order {
void execute();
}
// 第2步,创建一个请求对象
class Stock {
private String name = "ABC";
private int quantity = 10;
public void buy() {
System.out.println("Stock [ Name: " + name + ", Quantity: " + quantity + " ] bought");
}
public void sell() {
System.out.println("Stock [ Name: " + name + ", Quantity: " + quantity + " ] sold");
}
}
// 第3步,创建实现Order接口的具体类
class BuyStock implements Order {
private Stock abcStock;
public BuyStock(Stock abcStock) {
this.abcStock = abcStock;
}
public void execute() {
abcStock.buy();
}
}
class SellStock implements Order {
private Stock abcStock;
public SellStock(Stock abcStock) {
this.abcStock = abcStock;
}
public void execute() {
abcStock.sell();
}
}
// 第4步,创建命令调用程序类
class Broker {
private List orderList = new ArrayList();
public void takeOrder(Order order) {
orderList.add(order);
}
public void placeOrders() {
for (Order order : orderList) {
order.execute();
}
orderList.clear();
}
}
public class Test {
public static void main(String[] args) {
Stock abcStock = new Stock();
BuyStock buyStockOrder = new BuyStock(abcStock);
SellStock sellStockOrder = new SellStock(abcStock);
Broker broker = new Broker();
broker.takeOrder(buyStockOrder);
broker.takeOrder(sellStockOrder);
broker.placeOrders();
}
}
运行结果:
Stock [ Name: ABC, Quantity: 10 ] bought
Stock [ Name: ABC, Quantity: 10 ] sold