double dispatcher

本文介绍了一个简单的Java面向对象编程实例——动物喂食系统,通过定义抽象类Animal、具体类Dog和Cat,实现了不同动物的喂食功能。通过实现接口和绑定喂食器,展示了Java面向对象设计的灵活性。

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public class Feeder {
public void feed(Animal animal) {
System.out.println("feed Animal.");
}
public void feed(Dog dog) {
System.out.println("feed Dog: " + dog.eat());
}
public void feed(Cat cat) {
System.out.println("feed Cat: " + cat.eat());
}
}


public interface Animal {
String eat();
}

public class Dog implements Animal {

@Override
public String eat() {
return "骨头";
}

}


public class Main {

public static void main(String[] args) {
Animal a = new Dog();
Feeder feeder = new Feeder();
feeder.feed(a);//print: feed Animal.
}

}


public interface Animal {
String eat();
void bindFeeder(Feeder feeder);
}
public class Dog implements Animal {

@Override
public String eat() {
return "骨头";
}

@Override
public void bindFeeder(Feeder feeder) {
feeder.feed(this);
}

}
public class Main {

public static void main(String[] args) {
Animal a = new Dog();
Feeder feeder = new Feeder();
a.bindFeeder(feeder);//print:feed Dog: 骨头
}

}
package com.cyh.www; import jakarta.servlet.RequestDispatcher; import jakarta.servlet.ServletException; import jakarta.servlet.annotation.WebServlet; import jakarta.servlet.http.HttpServlet; import jakarta.servlet.http.HttpServletRequest; import jakarta.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet(name = "cyh", urlPatterns = "/abcde") public class cyh extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // 首次访问时显示输入表单 if (req.getParameter("num1") == null) { RequestDispatcher dispatcher = req.getRequestDispatcher("index.jsp"); dispatcher.forward(req, resp); return; } try { // 获取用户输入 double num1 = Double.parseDouble(req.getParameter("num1")); double num2 = Double.parseDouble(req.getParameter("num2")); String operator = req.getParameter("operator"); // 创建Third实例并调用计算方法 Third calculator = new Third(); // 正常实例化 double result = calculator.calculate(num1, num2, operator); // 设置结果属性 req.setAttribute("num1", num1); req.setAttribute("num2", num2); req.setAttribute("operator", operator); req.setAttribute("result", result); // 转发到结果页面 RequestDispatcher dispatcher = req.getRequestDispatcher("result.jsp"); dispatcher.forward(req, resp); } catch (NumberFormatException e) { req.setAttribute("error", "请输入有效的数字"); RequestDispatcher dispatcher = req.getRequestDispatcher("index.jsp"); dispatcher.forward(req, resp); } catch (Exception e) { req.setAttribute("error", e.getMessage()); RequestDispatcher dispatcher = req.getRequestDispatcher("index.jsp"); dispatcher.forward(req, resp); } } // 添加doPost方法以支持表单提交 @Override protected void doPost 为什么请求的资源[/untitled1_war_exploded/webapp/abcde]不可用
07-08
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