code: public static void minus(double[] y, double[] x) {
          if (x.length != y.length) {
              throw new IllegalArgumentException(String.format("Arrays have different length: x[%d], y[%d]", x.length, y.length));
          }
  
          for (int i = 0; i < x.length; i++) {
              y[i] -= x[i];
          }
      }
docs: Element-wise subtraction of two arrays y = y - x.
  @param y minuend matrix
  @param x subtrahend matrix