JAVA面向对象题。

这个是我刚刚写的，可以直接运行的。应该能够满足你的需求吧。

public class Circle {

private float r;
private final static double PI = Math.PI;

Circle()
{
this.r = 1;

}
Circle(float radius)
{
this.r = radius;

}
private double getPerimeter()
{

return PI*2*r;
}
private double getArea()
{
return PI*r*r;
}
private double getRadius()
{
return r;
}
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Circle myCircle = new Circle(3);
System.out.println("Radius is "+myCircle.getRadius()+" Perimeter is "+myCircle.getPerimeter()+" Area is "+myCircle.getArea());
}
}

public class Circle {
private static final double PI=3.14;//常量PI
private int r;//半径

//无参构造器
public Circle() {
this.r=1;
}

//有参构造器
public Circle(int r) {
this.r = r;
}

//计算周长
public double getPerimeter(int r) {
double perimeter = 0;
perimeter = 2 * PI * r;
return perimeter;
}

//计算面积
public double getArea(int r) {
double area = 0;
area = PI * r * r;
return area;
}

public int getR() {
return r;
}
public void setR(int r) {
this.r = r;
}
}
希望对你有帮助~

public class Rectangle
{
private double width;
private double height;

//无参构造器
public Rectangle()
{}
//有参构造器
public Rectangle(double width, double height)
{
this.width = width;
this.height = height;
}
//属性的get和set方法定义
public void setWidth(double width)
{
this.width = width;
}

public double getWidth()
{
return this.width;
}

public void setHeight(double height)
{
this.height = height;
}
public double getHeight()
{
return this.height;
}
//计算周长的方法
private double getPerimeter()
{
return (width+height)*2;
}
//计算面积的方法
private double getArea()
{
return width*height;
}

public static void main(String[] args)
{
Rectangle rec = new Rectangle(3.6,5.8);
System.out.println("The perimeter of Rectangle is:"+rec.getPerimeter());
System.out.println("The area of Rectangle is:"+rec.getArea());
}
}

public class Circle{
     double area,round;
     double r;
     final double PI=Math.PI;
     public Circle(){
         r=1.0;
     }
     public Circle(double i){
         this.r=i;
     }

     public double getArea(double r){
         area=PI*r*r;
         return area;
     }
     public double getRound(double r){
         round=PI*r*2;
         return round;
     }
}