CSCI 401 ~ Homework # 5

// Name         :   Kyle Blanchard
// Due          :   10/1/2014
// Class        :   CSCI-401
// Assignment       :   Matrix Inverse ~ Homework # 5
// Contact      :   Kwblanchard@student.stcc.edu

// package csci401;

import java.util.Scanner;

public class Homework5 {

    public static void main(String[] args) {

        @SuppressWarnings("resource")
        Scanner input = new Scanner(System.in);
        System.out.print("Enter a11, a12, a13, a21, a22, a23, a31, a32, a33: ");

        // Assigns the user entered values to a 3x3 Matrix called A
        double[][] A = new double[3][3];
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                A[i][j] = input.nextDouble();
                }
        }

        // Gets the inverse of Matrix A
        double[][] Ainverse = inverse(A);
        // If there is no inverse matrix display the message saying so. If there is a matrix, print it.
        if (Ainverse == null)
            System.out.println("Unable to create an inverse matrix!");
        else
            displayInverse(Ainverse);
    }

    public static double[][] inverse(double[][] A) {

        // Gets the value of the Determinate using the formula  aei+_bfg-cdh-ceg-bdi-afh
        double determinant =  (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]);
        if (determinant == 0)
            return null;
        else {
        // Gets the Inverse matrix of Matrix A using the given formula
            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 < 3; i++) {
                for (int j = 0; j < 3; j++) {
                    inverse[i][j] = ( inverse[i][j] / determinant ) ;
                }
            }
            return inverse;
        }
    }

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

        // Prints each character of the inverse matrix followed by a space and a line break every 3 characters
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++)
                System.out.print(A[i][j] + " ");
            System.out.println("");
        }
    }
}