code: static Style get(final GridParam params) {
          final StyleBuilder builder = new StyleBuilder();
  
          final Symbolizer pointSymbolizer = crossSymbolizer("shape://plus", builder, CROSS_SIZE,
                                                             params.gridColor);
          final Style style = builder.createStyle(pointSymbolizer);
          final List<Symbolizer> symbolizers = style.featureTypeStyles().get(0).rules().get(0).symbolizers();
  
          if (params.haloRadius > 0.0) {
              Symbolizer halo = crossSymbolizer("cross", builder, CROSS_SIZE + params.haloRadius * 2.0,
                                                params.haloColor);
              symbolizers.add(0, halo);
          }
  
          return style;
      }
docs: Create the Grid Point style.