2つのベクトル(配列)ポイント対ポイント加算(Java)

public class CMatrix {
    private CMatrix() {}

    /**
     * addition of two vectors.
     *
     * @param x one vector
     * @param y another vector
     * @return result vector
     */
    public static int[] add(int[] x, int[] y) {
        matrixNotNull(x, y);
        int m1 = x.length;
        int m2 = y.length;
        vectorNotEmpty(m1, m2);
        matrixNotMismatching(m1, m2);
        int[] add = new int[m1];
        for (int i = 0; i < m1; i++) {
            add[i] = x[i] + y[i];
        }
        return add;
    }

    // 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); }
}