java语言程序设计 李元朝 第7章 类的继承和多态机制 练习题答案

class Tiff {
public Tiff(){ };
double calculate(float r)
{
return Math.PI*r*r;
}
double calculate(float r,float h)
{
return Math.PI*r*r*h;
}
public static void main(String args[])
{
Tiff tiff=new Tiff();
System.out.println("Area="+tiff.calculate(12.6f));
System.out.println("Volume="+tiff.calculate(12.6f,37.8f));
}
}

class CCircle {
protected double radius;
public CCircle(double r)
{
radius=r;
}
public void show()
{
System.out.println("Radius="+radius);
}
}

class CCoin {
private int value;
public CCoin(double r, int v)
{
super(r);
value=v;
}
public void show()
{
System.out.println("Radius="+radius+" Value="+value);
}
public static void main(String[] args)
{
CCircle circle=new CCircle(2.0);
CCoin coin=new CCoin(3.0,5);
circle.show();
coin.show();
}
}

class Parent {
protected int x;
public Parent(int i)
{
x=i;
}
int getX() { return x; }
void show()
{
System.out.println("x="+x);
}
}

class Son {
protected int x;
public Son(int j)
{
super(3); //调用父类的构造方法
this.x=j; //引用子类中的成员变量x
}
void show()
{
System.out.println("super.x="+super.x+" "+"this.x="+x);
//分别输出父类和子类的成员变量x
}

public static void main(String args[])
{
Son son=new Son(5);
son.show();
}
}

car,继承自vehicle。car中增加了属性：座位数passenger,增加了设置和获取座位数的方法，创建car的对象，为其设置新速度和颜色，并显示其状态（所有属性)
class Vehicle {
String color;
String kind;
int speed;
Vehicle() //默认构造方法
{
color="";
kind="";
speed=0;
}
public void setColor(String color1)
{
color=color1;
}
public void setSpeed(int speed1)
{
speed=speed1;
}
public void setKind(String kind1)
{
kind=kind1;
}
public String getColor()
{
return color;
}
public String getKind()
{
return kind;
}
public int getSpeed()
{
return speed;
}
}

class Car extends Vehicle {
int passenger;
public Car() //默认构造函数
{
super();
passenger=0;
}
public void setPassenger(int passenger)
{
this.passenger=passenger;
}
public int getPassenger()
{
return passenger;
}
public static void main(String[] args)
{
Car Benz=new Car();
Benz.setColor("Yellow");
Benz.setKind("Roadster");
Benz.setSpeed(120);
Benz.setPassenger(4);
System.out.println("Benz: ");
System.out.println("Color "+Benz.getColor());
System.out.print("Speed (km/h)");
System.out.println(Benz.getSpeed());
System.out.println("Kind "+Benz.getKind());
System.out.print("Passenger ");
System.out.println(Benz.getPassenger());
}
}

class Circle {
double x;
double y;
double r;
Circle(double x,double y,double r)
{
this.x=x;
this.y=y;
this.r=r;
}
public void setX(double x)
{
this.x=x;
}
public void setY(double y)
{
this.y=y;
}
public void setR (double r)
{
this.r=r;
}
public double getX()
{
return x;
}
public double getY()
{
return y;
}
public double getR ()
{
return r;
}
public double area()
{
return r*r*3.1416;
}
public double perimeter()
{
return 2*r*3.1416;
}
public void show()
{
System.out.print("x="+x+", y="+y+", Radius="+r);
}
}
class Cylinder extends Circle {
double h;
Cylinder(double x,double y,double r,double h)
{
super(x,y,r);
this.h=h;
}
public void setH (double h)
{
this.h=h;
}
public double getH ()
{
return h;
}
public double area() //计算圆柱体的表面积，覆盖了父类的area()函数
{
return perimeter()*h+super.area()*2;
}
public double volume() //计算圆柱体的体积
{
return super.area()*h;
}

public static void main(String[] args)
{
Cylinder cylinder=new Cylinder(1,1,4,8);
cylinder.show();
System.out.println(", Height="+cylinder.getH ());
System.out.println("Area="+cylinder.area());
System.out.println("Volume="+cylinder.volume());
}
}