求不同图形的周长（Java实训）

实训目的：

利用接口来实现多态。

实训要求：

设计一个图形的接口，接口含求周长的抽象方法，通过定义
不同图形如圆、矩形、三角形、梯形等类来实现接口中方法。通过接口类对
象引用子类对象来求不同图形的周长。

circular.java

package program2

public class circular implements Shape {
	double PI=3.1415926
	public double circular(double r) {
		// TODO Auto-generated method stub
		return 2*PI*r
	}
	@Override
	public double rectangular(double a, double b) {
		// TODO Auto-generated method stub
		return 0
	}
	@Override
	public double triangle(double a, double b, double c) {
		// TODO Auto-generated method stub
		return 0
	}
	@Override
	public double trapezoidal(double a, double b, double c, double d) {
		// TODO Auto-generated method stub
		return 0
	}

}

rectangular.java

package program2

public class rectangular implements Shape {

	@Override
	public double rectangular(double a,double b) {
		// TODO Auto-generated method stub
		return a*2+b*2
	}

	@Override
	public double circular(double r) {
		// TODO Auto-generated method stub
		return 0
	}

	@Override
	public double triangle(double a, double b, double c) {
		// TODO Auto-generated method stub
		return 0
	}

	@Override
	public double trapezoidal(double a, double b, double c, double d) {
		// TODO Auto-generated method stub
		return 0
	}


}

Shape.java

package program2

public interface Shape {
	double circular(double r)
	double rectangular(double a,double b)
	double triangle(double a,double b,double c)
	double trapezoidal(double a,double b,double c,double d)
}

Test.java

package program2

import java.util.Scanner

public class Test {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc=new Scanner(System.in)
		int flag
		System.out.println("请选择要计算图形的周长：")
		System.out.println("1：圆的周长：")
		System.out.println("2：矩形的周长：")
		System.out.println("3：三角形的周长：")
		System.out.println("4：梯形的周长：")
		flag=sc.nextInt()
		if(flag==1)
		{
			double r
			System.out.println("请输入圆的半径r：")
			r=sc.nextDouble()
			Shape C=new circular()
			System.out.println("圆的周长为："+C.circular(r))
		}
		if(flag==2)
		{
			double a,b
			System.out.println("请输入矩形的长：")
			a=sc.nextDouble()
			System.out.println("矩形的周长为："+"请输入矩形的宽：")
			b=sc.nextDouble()
			Shape C=new rectangular()
			System.out.println(C.rectangular(a,b))
		}
		if(flag==3)
		{
			double a,b,c
			System.out.println("请输入三角形的边长1：")
			a=sc.nextDouble()
			System.out.println("请输入三角形的边长2：")
			b=sc.nextDouble()
			System.out.println("请输入三角形的边长3：")
			c=sc.nextDouble()
			Shape C=new triangle()
			System.out.println("三角形的周长为："+C.triangle(a,b,c))
		}
		if(flag==4)
		{
			double a,b,c,d
			System.out.println("请输入梯形的底：")
			a=sc.nextDouble()
			System.out.println("请输入梯形的高：")
			b=sc.nextDouble()
			System.out.println("请输入梯形的腰1：")
			c=sc.nextDouble()
			System.out.println("请输入梯形的腰2：")
			d=sc.nextDouble()
			Shape C=new trapezoidal()
			System.out.println("梯形的周长为:"+C.trapezoidal(a,b,c,d))
		}
	}

}

trapezoidal.java

package program2

public class trapezoidal implements Shape {

	@Override
	public double circular(double r) {
		// TODO Auto-generated method stub
		return 0
	}

	@Override
	public double rectangular(double a, double b) {
		// TODO Auto-generated method stub
		return 0
	}

	@Override
	public double triangle(double a, double b, double c) {
		// TODO Auto-generated method stub
		return 0
	}

	@Override
	public double trapezoidal(double a, double b, double c, double d) {
		// TODO Auto-generated method stub
		return a+b+c+d
	}

}

triangle.java

package program2

public class triangle implements Shape {

	@Override
	public double circular(double r) {
		// TODO Auto-generated method stub
		return 0
	}

	@Override
	public double rectangular(double a, double b) {
		// TODO Auto-generated method stub
		return 0
	}

	@Override
	public double triangle(double a, double b, double c) {
		// TODO Auto-generated method stub
		return a+b+c
	}

	@Override
	public double trapezoidal(double a, double b, double c, double d) {
		// TODO Auto-generated method stub
		return 0
	}

}