定义圆和长方形2个类,并比较2个图形的面积大小,怎么用JAVA程序写?

import java.lang.math;
class Round{
private double r;
public void setValue(double r)
{ this.r = r; }
public double getArea()
{ return Math.PI*this.r*this.r; }
}
class Retan{
private double l;
private double w;
public void setValue(double l,double w)
{ this.l = l; this.w = w ; }
public double getArea()
{ return this.l*this.w; }
}
class Compare{
public static void compare(double a,double b)
{
if(a>b) System.out.println("第一个数较大");
if(a==b)System.out.println("相等");
if(a