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May 2000



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Exception: Check for correctness

Posted by LEMI on May 16, 2000 at 9:48 AM

Title: Exception Handling.
The Programm is to define a class Calculate, which contains the "main method" (public static void main(String[] arg) and has to function like this:

java Calculate "Object" "Area/Circumfrence""Data"
"Object" is Parallelogram, Rectangle or Square.
"Area/Circumfrence" is Area or Circumfrence.
"Data" is Parallelogram:"Side1", "Side2", Angle.
Rectangle:"Side1", "Side2"

Do I have to join al the three classes together? How do I add the main METHOD then? The programe are under. How can it then be interrupted with "throw new error();" as well give information to the user?


public class Parallelogramm {

private Koordinate k1,k2;
private double a,b,h;
private double alpha;

public Parallelogramm(Koordinate k1, Koordinate k2, double alpha) {
this.k1 = k1;
this.k2 = k2;
this.alpha = alpha;
h = Math.abs(k2.getY()-k1.getY());
b = h / Math.sin(alpha);
a = Math.abs(k2.getX()-k1.getX()) - b*Math.cos(alpha);

public Parallelogramm(Koordinate k1, Koordinate k2, int alpha) {

public double getA() { return a; }

public double getB() { return b; }

public double getH() { return h; }

public double getAlpha() { return alpha; }

public double Area() {
return a*h;

public double Circumfrence() {
return 2*(a+b);


public class Rectangle extends Parallelogramm {

public Rectangle(Koordinate k1, Koordinate k2) {
super(k1,k2,90); // alternativ: super(k1,k2,Math.PI/2);


public class Square extends Rectangle {

public Square(Koordinate k1, Koordinate k2) {
if (Math.abs(this.getSeite1()-this.getSeite2())>0.0001) {
throw new Error("The Coordinates do not describe a Square");



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