public class Circle
{
private double radius
private static int numberOfObjects
public Circle()
{
numberOfObjects++
}
public Circle(double radius)
{
numberOfObjects++
this.radius = radius
}
public void setRadius(double radius) {
this.radius = radius
}
public double getRadius() {
return radius
}
public static int getNumberOfObjects() {
return numberOfObjects
}
public double getArea()
{
return Math.PI * radius * radius
}
}
----------------------------------------------------------------------
public static void main(String[] args)
{
Circle circle1 = new Circle(5)
Circle circle2 = new Circle()
circle2.setRadius(6)
System.out.println("第一个圆的半径 = " + circle1.getRadius() + "面积 = "+ circle1.getArea())
System.out.println("第二个圆的半径 = " + circle2.getRadius() + "面积 = "+ circle2.getArea())
System.out.println("总共有几个圆的对象 = " + Circle.getNumberOfObjects())
}
