P. 125 Ex. 12.7

// Shavit Borisov
// CW

import java.util.Scanner;

public class Main {

    public static void main(String[] args)
    {
        final int SIZE = 3;

        Scanner in = new Scanner(System.in);

        int value;

        System.out.printf("The size of your matrix is %d.\n", SIZE);
        MagicMatrix matrix = new MagicMatrix(SIZE);

        System.out.printf("Start entering values into your matrix:\n");
        for(int i = 0; i < SIZE; i++)
            for(int j = 0; j < SIZE; j++)
            {
                System.out.printf("matrix[%d][%d] = ", i, j);
                value = in.nextInt();
                matrix.updateCell(i, j, value);
            }
        System.out.printf("%s", matrix.equalRows() ? "Your matrix has equal rows\n" : "Your matrix doesn't have equal rows\n");
        System.out.printf("%s", matrix.equalCols() ? "Your matrix has equal cols\n" : "Your matrix doesn't have equal cols\n");
        System.out.printf("%s", matrix.magicMatrix() ? "Your matrix is magical" : "Your matrix isn't magical");

        in.close();
    }
}

// Next class

public class MagicMatrix
{
    int[][] matrix;

    public MagicMatrix(int size)
    {
        matrix = new int[size][size];
        for(int i = 0; i < size; i++)
            for(int j = 0; j < size; j++)
                matrix[i][j] = 0;
    }

    public void updateCell(int row, int col, int value)
    {
        matrix[row][col] = value;
    }

    public boolean equalRows()
    {
        boolean equal = true;
        int[] results = new int[matrix.length];
        for(int i = 0; i < results.length; i++)
            results[i] = 0;
        for(int i = 0; i < matrix.length; i++)
            for(int j = 0; j < matrix[i].length; j++)
                results[i] += matrix[i][j];
        for(int i = 0; (i < results.length - 1) && (equal); i++)
            if(results[i] != results[i + 1])
                equal = false;
        return equal;
    }

    public boolean equalCols()
    {
        boolean equal = true;
        int[] results = new int[matrix[0].length];
        for(int i = 0; i < results.length; i++)
            results[i] = 0;
        for(int j = 0; j < matrix[0].length; j++)
            for(int i = 0; i < matrix.length; i++)
                results[j] += matrix[i][j];
        for(int i = 0; (i < results.length - 1) && (equal); i++)
            if(results[i] != results[i + 1])
                equal = false;
        return equal;
    }

    public boolean magicMatrix()
    {
        if(equalRows() && equalCols())
        {
            int sum = 0;
            for(int i = 0; i < matrix.length; i++)
                sum += matrix[i][i];
            for(int i = 0; i < matrix.length; i++)
                sum -= matrix[0][matrix.length - i - 1];
            if(sum == 0)
            {
                for(int i = 0; i < matrix.length; i++)
                    sum += matrix[0][i];
                for(int i = 0; i < matrix[0].length; i++)
                    sum -= matrix[i][0];
                if(sum == 0)
                    return true;
            }
        }
        return false;
    }
}