ArraysTask10IdentityMatrixChecker.java

package HomeWork;

/**
 * Created by Andrey on 02.01.2016.
 */
public class ArraysTask10IdentityMatrixChecker {
    public static void main(String[] args) {

        int[][] matrix = {{1, 0, 0}, {0, 1, 0}, {0, 0, 1}};
//        int[][] matrix = {{1, 0, 2}, {0, 1, 0}, {2, 0, 1}};
//        int[][] matrix = {{1, 0, 0}, {0, 1, 0}, {0, 0, 1}, {0, 0, 0}};
        System.out.println(isIndetity(matrix));
    }

    public static boolean isIndetity(int[][] matrix) {
        checkRowsCols(matrix);
        int check = 0;
        int elemIdentity = 1;
        int count = 0;
        for (int i = 0; i < matrix.length; i++) {
            if (matrix[i][i] == elemIdentity) count++;
            for (int j = 0; j <matrix[i].length ; j++) {
                if (matrix[i][j]>0)check++;
            }
        }
        boolean identity = (matrix.length == count && count == check);
        return identity;
    }

    public static void checkRowsCols(int[][] matrix) {
        int rows = 0;
        int cols = 0;
        for (int i = 0; i < matrix.length; i++) {
            rows++;
        }
        for (int i = 0; i < matrix[0].length; i++) {
            cols++;
        }
        if (rows != cols) {
            throw new IllegalArgumentException( "Your Array isn't cubic " );
        }
        return;
    }
}

ArraysTask3ArrayPositiveFinder.java

package HomeWork;

/**
 * Created by Andrey on 27.12.2015.
 */
public class ArraysTask3ArrayPositiveFinder {
    public static void main(String[] args) {
        int[] array = {-3, -5, 1, -4, 2, -5};
        System.out.println(findFirstPositive(array));
        System.out.println(findLastPositive(array));
    }

    public static int findFirstPositive(int[] array) {
        int result = 0;
        for (int i : array) {
            if (i > 0) break;
            result++;
            if (result == array.length) return -1;
        }
        return result;
    }

    public static int findLastPositive(int[] array) {
        int result = array.length - 1;
        for (int i = result; i > 0; i--) {
            if (array[i] > 0) break;
            result--;
            if (result == 0) return -1;
        }
        return result;
    }
}

ArraysTask8MatrixMaxSumRowFinder.java

package HomeWork;

/**
 * Created by Andrey on 30.12.2015.
 */
public class ArraysTask8MatrixMaxSumRowFinder {
    public static void main(String[] args) {

        int[][] matrix = {{0, 3, -2}, {2, 1, 3}, {-1, 5, 2}};

        System.out.println(findMaxSumRow(matrix));
    }

    public static int findMaxSumRow(int[][] matrix) {
        checkArray(matrix);
        int indexRow = -1;
        int count = 0;
        int maxSum = count;
        for (int i = 0; i < matrix.length; i++) {
            int sumRow = 0;
            for (int j = 0; j < matrix.length; j++) {
                sumRow = sumRow + matrix[i][j];
            }
            if (sumRow > maxSum) {
                maxSum = sumRow;
                indexRow++;
            }
        }
        return indexRow;
    }

    public static void checkArray(int[][] matrix) {
        if (matrix.length == 0) {
            throw new IllegalArgumentException(" Your Array has lenght 0 ");
        }return;
    }
}

ArraysTask9MatrixTransposer.java

package HomeWork;

/**
 * Created by Andrey on 01.01.2016.
 */
public class ArraysTask9MatrixTransposer {
    public static void main(String[] args) {
        int[][] sourceMatrix = {{1, 2, 3, 4, 9}, {5, 6, 7, 8,10}};
        transpose(sourceMatrix);
    }

    public static int[][] transpose(int[][] sourceMatrix) {
        int[][] transposeMatrix = new int[sourceMatrix[0].length][sourceMatrix.length];

        for (int i = 0; i < sourceMatrix[0].length; i++) {
            for (int j = 0; j < sourceMatrix.length; j++) {
                transposeMatrix[i][j] = sourceMatrix[j][i];
                System.out.print(transposeMatrix[i][j] + " ");
            }
            System.out.println();
        }
        return transposeMatrix;
    }
}