更新时间:2023-02-06 16:22:43
因为 JDBCCategoryDataset
实现了CategoryDataset
接口,赋值时不需要强制转换:CategoryDataset data = readData();
我从下面概述的 readData()
的变体中得到以下图表.我怀疑你有另一个问题.
Because JDBCCategoryDataset
implements the CategoryDataset
interface, no cast should be required in the assignment: CategoryDataset data = readData();
I get the following chart from the variation of readData()
outlined below. I suspect that you have another problem.
private CategoryDataset readData() {
JDBCCategoryDataset data = null;
Connection con;
try {
con = DriverManager.getConnection("jdbc:h2:mem:test", "", "");
data = new JDBCCategoryDataset(con);
String sql = "select TYPE_NAME, PRECISION "
+ "from INFORMATION_SCHEMA.TYPE_INFO "
+ "where PRECISION BETWEEN 1 AND 12";
data.executeQuery(sql);
con.close();
}
…
return data;
}