add 7 2 Halfway done

src/part7/aufg2/Anwendung.java

@@ -0,0 +1,23 @@
+package part7.aufg2;
+
+import part7.aufg2.shapes.*;
+
+public class Anwendung {
+    public static void main(String[] args) {
+        Circle round_robert = new Circle();
+
+        round_robert.setRadius(4);
+        System.out.println(round_robert.getArea());
+        System.out.println(round_robert.getCircumference());
+
+        round_robert.setRadius(5);
+        System.out.println(round_robert.getArea())
+        ;System.out.println(round_robert.getCircumference());
+
+        round_robert.setRadius(1);
+        System.out.println(round_robert.getArea());
+        System.out.println(round_robert.getCircumference());
+
+
+    }
+}

src/part7/aufg2/shapes/Circle.java

@@ -0,0 +1,31 @@
+package part7.aufg2.shapes;
+
+public class Circle extends Form {
+    private float radius;
+    private double area;
+    private double circumference;
+
+    public void setRadius(float radius){
+        this.radius = radius;
+        setArea(radius);
+        setCircumference(radius);
+    }
+    private void setArea(double radius){
+        this.area = Math.PI * Math.pow(getRadius(),2);
+    }
+
+    private void setCircumference(double radius){
+        this.circumference = Math.PI * 2 * getRadius();
+    }
+    public float getRadius() {
+        return radius;
+    }
+
+    public double getArea(){
+        return area;
+    }
+
+    public double getCircumference() {
+        return circumference;
+    }
+}

src/part7/aufg2/shapes/Form.java

@@ -0,0 +1,9 @@
+package part7.aufg2.shapes;
+
+abstract class Form {
+    private float circumference;
+    private float area;
+
+    abstract double getArea();
+    abstract double getCircumference();
+}

src/part7/aufg2/shapes/Regular_n_gon.java

@@ -0,0 +1,26 @@
+package part7.aufg2.shapes;
+
+public class Regular_n_gon extends Form{
+    private int edges;
+    private float sideLength;
+
+    public void setEdges(int edges) {
+        this.edges = edges;
+    }
+
+    public int getEdges() {
+        return edges;
+    }
+
+    public float getSideLength() {
+        return sideLength;
+    }
+
+    public double getCircumference(){
+        return getSideLength() * getEdges();
+    }
+
+    public double getArea() {
+        return 0;
+    }
+}