//应用程序,文件名为CircleDemo.java
class CircleDemo
{
public static void main(string[] args)
{
Circle myCircle=new Circle();
myCircle.setRadius(2.1);
System.out.println("the area of this Circle is "+myCircle.area());
}
}
class Circle
{
final double PI=3.14;
private double radius;
public void setRadius(double r)
{
radius=r;
}
public double area()
{
double area;
area=PI*radius*radius;
return area;
}
class CircleDemo
{
public static void main(string[] args)
{
Circle myCircle=new Circle();
myCircle.setRadius(2.1);
System.out.println("the area of this Circle is "+myCircle.area());
}
}
class Circle
{
final double PI=3.14;
private double radius;
public void setRadius(double r)
{
radius=r;
}
public double area()
{
double area;
area=PI*radius*radius;
return area;
}
class CircleDemo
{
public static void main(string[] args)
{
Circle myCircle=new Circle();
myCircle.setRadius(2.1); //将参数传递给r,r又赋值给radius, 则radius=2.1
System.out.println("the area of this Circle is "+myCircle.area()); //调用area()方法,进入area方法
}
}
class Circle
{
final double PI=3.14;
private double radius;
public void setRadius(double r)
{
radius=r;
}
public double area()
{
double area;
area=PI*radius*radius; // area = 3.14*2.1*2.1=13.8474
return area; //将已经有值为13.8474的变量area返回给上面的调用方法,则打印出13.8474
}