JFreeChart XYSeries出现问题

Question

我不确定为什么这里会发生错误？我正在使用JFreeChart API并尝试创建一个xy系列。我已经在代码下面添加了错误消息。主方法只是简单地调用这个方法来运行它

public class CreateGraph {
    private String fileInput="F:/FunctionTrader/testFiles/test1.txt";
    private XYSeries bunch=new XYSeries(null);
    public void test() throws FileNotFoundException, IOException {
        try (BufferedReader br = new BufferedReader(new FileReader(this.fileInput))) {
            String modBarVals;
            while ((modBarVals=br.readLine()) != null ){
                String[] split = modBarVals.split("\s+");
                double x = Double.parseDouble(split[0]);
                double y = Double.parseDouble(split[1]); 
                bunch.add(x,y); //error occurs here?
            }
            System.out.println(bunch.getItemCount());
        }
    }
}

异常堆栈跟踪：

Exception in thread "main" java.lang.ExceptionInInitializerError
    Caused by: java.lang.IllegalArgumentException: Null 'key' argument.
        at org.jfree.chart.util.ParamChecks.nullNotPermitted(ParamChecks.java:65)
        at org.jfree.data.general.Series.<init>(Series.java:120)
        at org.jfree.data.general.Series.<init>(Series.java:110)
        at org.jfree.data.xy.XYSeries.<init>(XYSeries.java:172)
        at org.jfree.data.xy.XYSeries.<init>(XYSeries.java:145)
        at IO2x.CreateGraph.<init>(CreateGraph.java:17)
        at IO2x.MainClass.<clinit>(MainClass.java:17)

Answer 1

stacktrace告诉您不能在for XYSeries中使用null Comparable键。你可以使用

private XYSeries bunch = new XYSeries("My Data");