2つのベクトル(配列)の乗算(Java)

2つのベクトル(配列)の乗算(Java)
 

public class CMatrix {
    private CMatrix() {}

    /**
     * Dot multiplication of two vectors.
     *
     * @param x one vector
     * @param y another vector
     * @return resykt of dot multiplication
     */
    public static int dot(int[] x, int[] y) {
        matrixNotNull(x, y);
        vectorNotEmpty(x.length, y.length);
        matrixNotMismatching(x.length, y.length);
        int dot = 0;
        for (int i = 0; i < x.length; i++) {
            dot += x[i] * y[i];
        }
        return dot;
    }

    /**
     * Dot multiplication of two vectors.
     *
     * @param x one vector
     * @param y another vector
     * @return resykt of dot multiplication
     */
    public static double dot(double[] x, double[] y) {
        matrixNotNull(x, y);
        vectorNotEmpty(x.length, y.length);
        matrixNotMismatching(x.length, y.length);
        double dot = 0;
        for (int i = 0; i < x.length; i++) {
            dot += x[i] * y[i];
        }
        return dot;
    }

    // throw an IllegalArgumentException if obj is null
    // (obj is any type of array)
    private static void matrixNotNull(Object... obj) {
        for (Object o : obj) {
            if (o == null)
                throw new IllegalArgumentException("matrix is null");
        }
    }

    // Check if the vectors are not empty.
    private static void vectorNotEmpty(int... lens) {
        for (int len : lens) {
            if (len == 0)
                throw new EmptyVectorException();
        }
    }

    // Check if the two matrices are mismatch the number of rows.
    private static void matrixNotMismatching(int n, int m) {
        if (n != m)
            throw new MismatchingMatrixException();
    }
}

class EmptyVectorException extends RuntimeException {
    public EmptyVectorException() { super(); }

    public EmptyVectorException(String s) { super(s); }
}

class MismatchingMatrixException extends RuntimeException {

    public MismatchingMatrixException() { super(); }

    public MismatchingMatrixException(String s) { super(s); }
}