JFreeChart柱状图单组柱子的不同颜色显示

JFreeChart柱状图中单组柱子用不同颜色来显示的实现方法是自定义一个Renderer来继承BarRenderer类，然后重载getItemPaint(int i,int j)方法。

实现效果如下：

实现代码如下：

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public class CustomRenderer extends org.jfree.chart.renderer.category.BarRenderer {          /**       *        */      private static final long serialVersionUID = 784630226449158436L;      private Paint[] colors;      //初始化柱子颜色      private String[] colorValues = { "#AFD8F8", "#F6BD0F", "#8BBA00", "#FF8E46", "#008E8E", "#D64646" };          public CustomRenderer() {          colors = new Paint[colorValues.length];          for (int i = 0; i < colorValues.length; i++) {              colors[i] = Color.decode(colorValues[i]);          }      }          //每根柱子以初始化的颜色不断轮循      public Paint getItemPaint(int i, int j) {          return colors[j % colors.length];      }  }

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public class CreateJFreeChartBarColor {          /**       * 创建JFreeChart Bar Chart（柱状图）       */      public static void main(String[] args) {          // 步骤1：创建CategoryDataset对象（准备数据）          CategoryDataset dataset = createDataset();          // 步骤2：根据Dataset 生成JFreeChart对象，以及做相应的设置          JFreeChart freeChart = createChart(dataset);          // 步骤3：将JFreeChart对象输出到文件，Servlet输出流等          saveAsFile(freeChart, "E:\\bar.png", 500, 400);      }          // 保存为文件      public static void saveAsFile(JFreeChart chart, String outputPath, int weight, int height) {          FileOutputStream out = null;          try {              File outFile = new File(outputPath);              if (!outFile.getParentFile().exists()) {                  outFile.getParentFile().mkdirs();              }              out = new FileOutputStream(outputPath);              // 保存为PNG文件              ChartUtilities.writeChartAsPNG(out, chart, weight, height);              out.flush();          } catch (FileNotFoundException e) {              e.printStackTrace();          } catch (IOException e) {              e.printStackTrace();          } finally {              if (out != null) {                  try {                      out.close();                  } catch (IOException e) {                      // do nothing                  }              }          }      }          // 根据CategoryDataset生成JFreeChart对象      public static JFreeChart createChart(CategoryDataset categoryDataset) {          JFreeChart jfreechart = ChartFactory.createBarChart("学生统计图", // 标题                  "学生姓名", // categoryAxisLabel （category轴，横轴，X轴的标签）                  "年龄", // valueAxisLabel（value轴，纵轴，Y轴的标签）                  categoryDataset, // dataset                  PlotOrientation.VERTICAL, false, // legend                  false, // tooltips                  false); // URLs              Font labelFont = new Font("SansSerif", Font.TRUETYPE_FONT, 12);              jfreechart.setTextAntiAlias(false);          jfreechart.setBackgroundPaint(Color.white);              CategoryPlot plot = jfreechart.getCategoryPlot();// 获得图表区域对象              // 设置横虚线可见          plot.setRangeGridlinesVisible(true);          // 虚线色彩          plot.setRangeGridlinePaint(Color.gray);          // 数据轴精度          NumberAxis vn = (NumberAxis) plot.getRangeAxis();          // vn.setAutoRangeIncludesZero(true);          DecimalFormat df = new DecimalFormat("#0.0");          vn.setNumberFormatOverride(df); // 数据轴数据标签的显示格式              // x轴设置          CategoryAxis domainAxis = plot.getDomainAxis();          domainAxis.setLabelFont(labelFont);// 轴标题          domainAxis.setTickLabelFont(labelFont);// 轴数值          // Lable（Math.PI/3.0）度倾斜          // domainAxis.setCategoryLabelPositions(CategoryLabelPositions          // .createUpRotationLabelPositions(Math.PI / 3.0));          domainAxis.setMaximumCategoryLabelWidthRatio(6.00f);// 横轴上的 Lable          // 是否完整显示              // 设置距离图片左端距离          domainAxis.setLowerMargin(0.1);          // 设置距离图片右端距离          domainAxis.setUpperMargin(0.1);          // 设置 columnKey 是否间隔显示          // domainAxis.setSkipCategoryLabelsToFit(true);          plot.setDomainAxis(domainAxis);          // 设置柱图背景色（注意，系统取色的时候要使用16位的模式来查看颜色编码，这样比较准确）          plot.setBackgroundPaint(new Color(255, 255, 204));              // y轴设置          ValueAxis rangeAxis = plot.getRangeAxis();          rangeAxis.setLabelFont(labelFont);          rangeAxis.setTickLabelFont(labelFont);          // 设置最高的一个 Item 与图片顶端的距离          rangeAxis.setUpperMargin(0.15);          // 设置最低的一个 Item 与图片底端的距离          rangeAxis.setLowerMargin(0.15);          plot.setRangeAxis(rangeAxis);              // 解决中文乱码问题(关键)          TextTitle textTitle = jfreechart.getTitle();          textTitle.setFont(new Font("黑体", Font.PLAIN, 20));          domainAxis.setTickLabelFont(new Font("sans-serif", Font.PLAIN, 11));          domainAxis.setLabelFont(new Font("宋体", Font.PLAIN, 12));          vn.setTickLabelFont(new Font("sans-serif", Font.PLAIN, 12));          vn.setLabelFont(new Font("黑体", Font.PLAIN, 12));          // jfreechart.getLegend().setItemFont(new Font("宋体", Font.PLAIN, 12));              // 使用自定义的渲染器                  CustomRenderer renderer = new CustomRenderer();          // 设置柱子宽度          renderer.setMaximumBarWidth(0.2);          // 设置柱子高度          renderer.setMinimumBarLength(0.2);          // 设置柱子边框颜色          renderer.setBaseOutlinePaint(Color.BLACK);          // 设置柱子边框可见          renderer.setDrawBarOutline(true);          // 设置每个地区所包含的平行柱的之间距离          renderer.setItemMargin(0.5);          jfreechart.getRenderingHints().put(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_OFF);          // 显示每个柱的数值，并修改该数值的字体属性          renderer.setIncludeBaseInRange(true);          renderer.setBaseItemLabelGenerator(new StandardCategoryItemLabelGenerator());          renderer.setBaseItemLabelsVisible(true);          plot.setRenderer(renderer);          // 设置柱的透明度          plot.setForegroundAlpha(1.0f);              // 背景色 透明度          plot.setBackgroundAlpha(0.5f);              return jfreechart;      }          // 创建CategoryDataset对象      public static CategoryDataset createDataset() {          double[][] data = new double[][] { { 25, 24, 40, 12, 33, 33 } };          String[] rowKeys = { "" };          String[] columnKeys = { "张三", "李四", "王五", "马六", "陈七", "赵八" };          CategoryDataset dataset = DatasetUtilities.createCategoryDataset(rowKeys, columnKeys, data);          return dataset;      }      }