MatrixInverse

import java.util.Scanner;


public class MatrixInverse {
    /*
     *
     * Luis Quinones
     * Assignment 5
     * Professor Silvestri
     *
     * Returns the inverse matrix of a given matrix
     *
     */

    public static double [][] inverse (double [][] A){
        double determinant = determinant(A);
        if(determinant==0)
            return null;
        else {


        double [][] inverse = {
                {A[1][1]*A[2][2] - A[1][2] * A[2][1], A[0][2]* A[2][1] - A[0][1]*A[2][2], A[0][1]*A[1][2] - A[0][2]*A[1][1]},
                {A[1][2]*A[2][0] - A[1][0] * A[2][2], A[0][0]* A[2][2] - A[0][2]*A[2][0], A[0][2]*A[1][0] - A[0][0]*A[1][2]},
                {A[1][0]*A[2][1] - A[1][1] * A[2][0], A[0][1]* A[2][0] - A[0][0]*A[2][1], A[0][0]*A[1][1] - A[0][1]*A[1][0]}
        };

        for (int i=0;i<inverse.length;i++){
            for(int j =0; j<inverse[i].length;j++)
            {
                inverse[i][j]/=determinant;
            }
        }
        return inverse;
    }
    }

    public static double determinant(double [][] A){
        return A[0][0] * A[1][1]*A[2][2] + A[2][0]*A[0][1]*A[1][2] + A[0][2]*A[1][0]*A[2][1] - A[0][2]*A[1][1]*A[2][0] - A[0][0]*A[1][2]*A[2][1] - A[2][2]* A[1][0]*A[0][1];
    }

    public static double [][] getInput()
    {
         Scanner sc = new Scanner(System.in);
         System.out.print("Enter a11, a12, a13, a21, a22, a23, a31, a32, a33: ");
        double [][] A = new double[3][3];
        for(int i=0; i<3;i++){
            for(int j=0; j<3; j++)
            {
                A[i][j] = sc.nextDouble();
            }
        }
        return A;
    }

    public static void printArray(double [][] A){

        for(int i=0;i<A.length;i++){
            for(int j=0;j<A[i].length;j++)
                System.out.print(A[i][j]+" ");
            System.out.println("");
        }
    }
    public static void main(String args[]){
        double [][]A = getInput();
        double [][]inverse = inverse(A);

        if(inverse==null)
            System.out.println("No inverse matrix");
        else
            printArray(inverse);
    }

}