public class Kreis
{
     private double radius;

     public void  setRadius( double rad ){
         radius = rad ;
     }
     public double getRadius(){
        return radius;
     }
     public double flaeche(){
        return Math.PI * radius * radius;
     }

     static public void main( String [] args )
     {
         Kreis kreis1 = new Kreis();
         kreis1.setRadius( 10 );
         System.out.println( "Der Radius betraegt " + kreis1.getRadius());
         System.out.println( "Die Flaeche  betraegt " + kreis1.flaeche());
     }
}