"java.lang.ClassCastException: org.apache.derby.client.net.NetConnection cannot be cast to smartdat

Question

我100%确信我的连接名称是正确的，"智能数据库"；是存在该代码的包；SmartData"；是我在NetBeansIDE8.2中的嵌入式数据库(我相信它是一个Derby数据库(。

package smartdatabase;
import java.sql.*;
import org.apache.derby.jdbc.EmbeddedDriver;
public class Connection {
private Connection conn = null;
private Statement stmt = null;
public Connection() {
}
public void getStudents() {
try {
Class.forName("org.apache.derby.jdbc.ClientDriver").newInstance();
conn = (Connection) 
DriverManager.getConnection("jdbc:derby://localhost:1527/SmartData;create=true;", "root", "The 
password");
`    `String sql;
sql = "SELECT Firstname, Surname FROM tblStudents";
ResultS``et rs = stmt.executeQuery(sql);
while (rs.next()) {
String Firstname = rs.getString("FirstName");
String Surname = rs.getString("Surname");
System.out.println(Firstname + "    " + Surname);
}
} catch (SQLException se) {
se.printStackTrace();
} catch (`Exception e) {
e.printStackTrace();
}
}
}

Answer 1

您的smartdatabase包中可能有一个名为Connection的类。使用此类而不是java.sql.Connection默认情况下，编译器从同一个包解析Connection。

尝试重命名该类或使用完全限定名称(java.sql.Connection(，而不是仅使用Connection:

private java.sql.Connection conn = null;