code: public Axis setAxisLabel(String label) {
          if (label == null) {
              if (index == 0) {
                  label = "X";
              } else if (index == 1) {
                  label = "Y";
              } else if (index == 2) {
                  label = "Z";
              }
          }
  
          if (label != null) {
              double[] position = new double[base.getDimension()];
  
              if (base.getDimension() == 2) {
                  position[index] = 0.5;
                  if (index == 0) {
                      position[1] = -0.1;
                      axisLabel = new BaseLabel(label, 0.5, 1.0, position);
                  } else {
                      position[0] = -0.15;
                      axisLabel = new BaseLabel(label, 0.5, 0.5, -Math.PI / 2, position);
                  }
              } else {
                  if (index == 0) {
                      position[2] = 1.0;
                      position[index] = 0.5;
                      axisLabel = new BaseLabel(label, 0.5, -2.0, position);
                  } else if (index == 1) {
                      position[0] = 1.0;
                      position[index] = 0.5;
                      axisLabel = new BaseLabel(label, 0.5, 3.0, position);
                  } else if (index == 2) {
                      position[1] = 1.0;
                      position[index] = 1.0;
                      axisLabel = new BaseLabel(label, -0.5, -1.0, position);
                  }
              }
  
              axisLabel.setFont(axisLabelFont);
          }
          return this;
      }
docs: Sets the label of this axis.