代理模式

【代理模式】为其他对象提供一种代理以控制对这个对象的访问

package com.demo.proxy;

public class Triangle implements Geometry {

	double a,b,c;
	public Triangle(double a,double b,double c){
		this.a=a;
		this.b=b;
		this.c=c;
	}
	@Override
	public double getArea() {
		// TODO Auto-generated method stub
		double p=(a+b+c)/2.0;
		return Math.sqrt(p*(p-a)*(p-b)*(p-c));
	}
}

package com.demo.proxy;

public class TriangleProxy implements Geometry {

	double a,b,c;
	Triangle triangle;
	public void setABC(double a,double b,double c){
		this.a=a;
		this.b=b;
		this.c=c;
	}
	@Override
	public double getArea() {
		// TODO Auto-generated method stub
		if(a+b>c&&a+c>b&&b+c>a){
			triangle=new Triangle(a,b,c);
			//让所代理的对象调用getArea()方法
			return triangle.getArea();
		}else
			return -1;
	}
}

package com.demo.proxy;

import java.util.Scanner;

public class Application {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner reader=new Scanner(System.in);
		System.out.println("请输入三个数，每输入一个数回车确认:");
		double a=-1,b=-1,c=-1;
		a=reader.nextDouble();
		b=reader.nextDouble();
		c=reader.nextDouble();
		TriangleProxy proxy=new TriangleProxy();
		proxy.setABC(a, b, c);
		double area=proxy.getArea();
		System.out.println("面积是："+area);
	}
}