abstractsample.java

接口和抽象类.rar

package chapter4;

/**
 * 抽象类的使用举例
 */
abstract class Shape {
	private static int n;
	/** 抽象类中的抽象方法 */
	abstract float getArea();
	/** 抽象类中也可以包含非抽象的方法 */
	public int getCount() {
		return n++;
	}
}

/**
 * 由抽象类Shape派生的具体子类--圆类
 */
class Circle extends Shape {
	public int r;
	Circle(int r) {
		this.r=r;
	}
	public float getArea() {
		return 3.14f*r*r;
	}
}

/**
 * 由抽象类Shape派生的具体子类--矩形类
 */
class Rectangle extends Shape {
	public int width,height; 
	Rectangle(int w, int h) {
		width=w;
		height=h;
	}
	public float getArea() {
		return width*height;
	}
}

public class AbstractSample {
	public static void main(String[] args) {
		Shape s1 = new Circle(2);
		Shape s2 = new Rectangle(2,3);
		float area1 = s1.getArea();
		float area2 = s2.getArea();
		System.out.println("Circle's Area="+area1);
		System.out.println("Rectangle's Area="+area2);
	}
}