继承与抽象编程.doc

实验五、继承与抽象编程
1．实验目的
（1）理解抽象类的意义和实际应用的一般模式，熟练掌握抽象类和抽象方法的定义以及抽象类的继承，尤其是子类是非抽象类的情况。
2．实验内容和步骤
（1） 设计一个抽象形状类Shape，包含一个getArea()抽象方法。
（2） 在Shape类基础上设计圆形、矩形、三角形和梯形四个子类，要求根据实际形状重写getArea()方法。
abstract class Shape
{
protected String name;
public Shape(String xm)
{
name = xm;
System.out.print("名称:"+name);
}
abstract public double getArea();
}
class Circle extends Shape
{
private final double PI = 3.14;
private double radius;
public Circle(String shapeName,double r)
{
super(shapeName);
radius = r;
}
public double getArea()
{
return PI*radius*radius;
}

}
class Rectangle extends Shape
{
private double width;
private double height;
public Rectangle(String shapeName,double width,double height)
{
super(shapeName);
this.width = width;
this.height = height;
}
public double getArea()
{
return width*height;
}
}
class Trapezoid extends Shape
{
private double height;
private double topline;
private double baseline;
public Trapezoid(String shapeName,double height,double topline,double
baseline)
{
super(shapeName);
this.height = height;
this.topline = topline;
this.baseline = baseline;
}
public double getArea()
{
return height*(topline+baseline)/2;
}
}
class Trangle extends Shape
{
private double baseline;
private double height;
public Trangle(String shapeName,double height,double baseline)
{
super(shapeName);
this.height = height;
this.baseline = baseline;
}
public double getArea()
{
return height*baseline/2;
}
}
public class AB
{
public static void main(String[] args)
{
Shape circle = new Circle("圆",5.0);
System.out.print(";面积="+circle.getArea());
System.out.print("\n");
Shape rect= new Rectangle("矩形",3.0,5.0);
System.out.print(";面积="+rect.getArea());
System.out.print("\n");
Shape trangle = new Trangle("三角形",4.2,5.5);
System.out.print(";面积="+trangle.getArea());
System.out.print("\n");
Shape trapezoid =new Trapezoid("梯形",5.0,4.0,9.0);
System.out.print(";面积="+trapezoid.getArea());
System.out.print("\n");
}
}

（3） 设计一个TestShape类，包含变量area（存储总面积）、静态方法countArea(Shape s)，该方法负责把参数中的形状面积加入到area中。在main函数中新建（2）中四种类型的对象s1、s2、s3、s4，通过调用countArea方法把四个对象面积累加到area中，最后输出area。
（4） 将形状类Shape改为接口，在不修改测试类TestShape的基础上，保证执行TestShape能够得到与实验四同样的结果。
interface IShape
{
final double PI = 3.14;
abstract public double getArea();
}
class Circle implements IShape
{
double radius;
public Circle(double r)
{
radius = r;
}
public double getArea()
{
return PI*radius*radius;
}
}
class Rectangle implements IShape
{
private double width;
private double height;
public Rectangle(double width,double height)
{
this.width = width;
this.height = height;
}
public double getArea()
{
return width*height;
}
}
class Trapezoid implements IShape
{
private double height;
private double topline;
private double baseline;
public Trapezoid(double height,double topline,double baseline)
{
this.height = height;
this.topline = topline;
this.baseline = baseline;
}
public double getArea()
{
return height*(topline+baseline)/2;
}
}
class Trangle implements IShape
{
private double baseline;
private double height;
public Trangle(double height,double baseline)
{
this.height = height;
this.baseline = baseline;
}
public double getArea()
{
return height*baseline/2;
}
}
public class ABCD
{
public static void main(String[] args)
{
IShape circle = new Circle(3.0);
System.out.print("圆面积="+circle.getArea());
System.out.print("\n");
Rectangle rect = new Rectangle(2.5,3.2);
System.out.print("矩形面积="+rect.getArea());
System.out.print("\n");
Trapezoid trapezoid =new Trapezoid(5.0,6.0,9.0);
System.out.print("梯形面积="+trapezoid.getArea());
System.out.print("\n");
Trangle trangle = new Trangle(6.0,5.0);
System.out.print("三角形面积="+trangle.getArea());
System.out.print("\n");
}
}