错误：不兼容的类型：float无法转换为XYZDataItem

Question

我从另一种方法获得XYZ点，我想将它们添加到
 private static XYZDataset createDataset()

我得到的错误是

incompatible types: float cannot be converted to XYZDataItem

如何解决错误？

这是我的代码：

private static XYZDataset createDataset() {
// current directory to read all the .txt files
    File currentDir = new File("C:\\Users\\user\\Desktop\\folder");
    String Sresult[];
    Sresult = displayContents(currentDir);
    String var = Sresult[0];
    float result[];
    result = readfile(var); //readfile to get the XYZ and I
    float xx = 0; float yy = 0; float zz = 0; float ii=0;
    for (int i = 0; i < var.length(); i++){
    //System.out.println(result[0]);
        xx = result[0];
        yy = result[1];
        zz = result[2];
        ii = result[3];
    }

    XYZSeries s1 = new XYZSeries("S1");
    for (int i = 0; i < 10000; i++) {
        s1.add(xx);                   //here is where the error occur.
    }

    XYZSeriesCollection dataset = new XYZSeriesCollection();
    dataset.add(s1);

    return dataset;
}