public class Vector {

    public static void scalarMultiplication(int[] vector, int scalar) {
        for (int position = 0; position < vector.length; position++) {
            vector[position] *= scalar;
        }
    }

    public static void vectorProduct(int[] vector1, int[] vector2) {

        if (vector1.length == vector2.length && vector2.length == 3) {
            int[] kreuzVektor3D = new int[3];
            kreuzVektor3D[0] = (vector1[1] * vector2[2]) - (vector1[2] * vector2[1]);
            kreuzVektor3D[1] = (vector1[2] * vector2[0]) - (vector1[0] * vector2[2]);
            kreuzVektor3D[2] = (vector1[0] * vector2[1]) - (vector1[1] * vector2[0]);
            System.out.println("Ergebnis des Kreuzproduktes: [" + kreuzVektor3D[0] + ", " + kreuzVektor3D[1] + ", "
                    + kreuzVektor3D[2] + "]");
        }

        else if (vector1.length == vector2.length && vector2.length == 2) {
            int kreuzVektor2D = 0;
            kreuzVektor2D = (vector1[0] * vector2[1]) - (vector1[1] * vector2[0]);
            System.out.println("Ergebnis des Kreuzproduktes: " + kreuzVektor2D);
        }

        else {
            System.out.println("Wegen unterschiedlichen Dimensionen ist das Kreuzprodukt nicht erlaubt");
        }
    }

    public static double vectorLength(int[] vector) {
        double qSumme = 0.0;
        double betrag = 0.0;
        for (int i = 0; i < vector.length; i++) {
            qSumme = qSumme + (vector[i] * vector[i]);
        }
        betrag = Math.sqrt(qSumme);

        return betrag;

    }

    public static int[][] matrixMultiplication(int[][] matrix, int scalar) {
        int[][] ausgabe;
        
        if (matrix == null){
            ausgabe = null;
        }
        else if (matrix.length == 3 && matrix[0].length == 3 && matrix[1].length == 3 && matrix[2].length == 3) {
            ausgabe = new int[3][3];
            for (int außenPos = 0; außenPos < matrix.length; außenPos++) {
                for (int innenPos = 0; innenPos < matrix[außenPos].length; innenPos++) {
                    ausgabe[außenPos][innenPos] = matrix[außenPos][innenPos] * scalar;
                }
            }
        
        }
        else {
            ausgabe = null;
        }

        return ausgabe;
    }

    public static void main(String[] args) {
        int[] vector = { 2, 4, 7 };
        int scalar = 3;
        scalarMultiplication(vector, scalar);
        System.out.println(vector[0] + " " + vector[1] + " " + vector[2]);

        int[] vector1 = { 2, 5, 1 };
        int[] vector2 = { 4, 7, 2 };

        vectorProduct(vector1, vector2);

        int[] vector3 = { 2, 5 };
        int[] vector4 = { 4, 7 };

        vectorProduct(vector3, vector4);
    }

}