code: private void setInput(double[] x) {
          if (x.length != inputLayer.units) {
              throw new IllegalArgumentException(String.format("Invalid input vector size: %d, expected: %d", x.length, inputLayer.units));
          }
          System.arraycopy(x, 0, inputLayer.output, 0, inputLayer.units);
      }
docs: Sets the input vector into the input layer.
  @param x the input vector.