abstractarea.java

Java 程序设计源码 只提供了部分

abstract class Figure {
	double dim1;
	double dim2;

	Figure(double a,double b) {
		dim1 = a;
		dim2 = b;
	}

	abstract double area();
}

class Rectangle extends Figure {
	Rectangle(double a,double b) {
		super(a,b);
	}
	
	double area() {
		return dim1 * dim2;
	}
}

class Triangle extends Figure {
	Triangle(double a,double b) {
		super(a,b);
	}

	double area() {
		return (dim1 * dim2) / 2;
	}
}

public class AbstractArea {
	public static void main(String[] args) {
		//Figure f = new Figure(); //illgel now 

		Rectangle r = new Rectangle(10,8);
		Triangle t = new Triangle(12,8);

		Figure f;
		Figure[] fi = new Figure[10];

		f = r;

		System.out.println(r.area());

		f = t;

		System.out.println(t.area());
	}
}