7.29 Java

熟悉掌握Java的语法 提高编程能力

package duotai;

import javax.xml.stream.events.Namespace;

abstract class Shape {
	public abstract double Getc();
	public abstract double Gets();
}

class Circle extends Shape{
	private double radius;
	public Circle(){
		this(0.0);// 等价于 this.radius = radius
	}
	public Circle(double radius) {
		this.radius = radius;
	}
	public double getRadius() {
		return radius;
	}
	@Override
	public double Gets() {
		double s = Math.PI * radius * radius;
		return s;
	}
	@Override
	public double Getc() {
		double c = 2.0 * Math.PI * radius;
		return c;
	}
	@Override
	public String toString(){
		return "[Circle] radius = " + radius;
	}
}

class Rectangle extends Shape{
	private double len;
	public Rectangle() {
		this(0.0);
	}
	public Rectangle(double len) {
		this.len = len; 
	}
	@Override
	public double Gets() {
		double s = len * len;
		return s;
	}
	@Override
	public double Getc() {
		double c = 4.0 * len;
		return c;
	}
	@Override
	public String toString() {
		return "[Rectangle] Side Length= " + len;
	}
}

public class Duotai {
	public static double Cal(Shape[] shapes) {
		double s = 0.0;
		for(Shape shape : shapes) {
			System.out.println(shape);
			s += shape.Gets();
		}
		return s;
	}
	public static void main(String[] args) {
		Shape[] shapes = new Shape[5];
		for(int i = 0; i < shapes.length; i++) {
			double d = Math.random();
			if(d < 0.5)shapes[i] = new Circle(1);
			else shapes[i] = new Rectangle(2);
		}
		double tot_s = Cal(shapes);
		System.out.println("tot sum = "+tot_s);
	}
}