java : non-static variable cannot be referenced from a static context Error

以下代码在变量con2上生成错误，说我在Google上搜索了"non-static variable con2 cannot be referenced from a static context Error."以获得解决方案，并且他们暗示尚未初始化该变量以使方法可用。我初始化不正确吗？我也尝试过将其更改为公开，但这也无济于事。

import java.io.*;
import java.net.*;

import java.sql.*;
import java.sql.CallableStatement;
import java.sql.ResultSet;
import java.sql.PreparedStatement;
import net.sourceforge.jtds.jdbcx.JtdsDataSource;
import net.sourceforge.jtds.jdbc.Driver;

class testconnect {

     private java.sql.Connection con2 = null;

     private final String url2 = "jdbc:jtds:sqlserver://";
     private final String serverName= "SQL01";
     private final String portNumber = "2677";
     private final String databaseName= "App";
     private final String userName = "bob";
     private final String password = "boob";
     private final String selectMethod = "cursor";

     private String getConnectionUrl2(){
        System.out.println("initalizing jtds");
          //String returnVal = url+serverName+":"+portNumber+";databaseName="+databaseName+";user="+userName+";password="+password+";instance="+instance+";";
          String returnVal = url2+serverName+":"+portNumber+"/"+databaseName+";user="+userName+";password="+password;
          System.out.println("url2: " + returnVal);
          return returnVal;
     }

     public static void main (String[] args) {
         con2 = java.sql.DriverManager.getConnection(getConnectionUrl2());

     }

} //end class

最佳答案

不，实际上，您必须声明con2字段为静态:

private static java.sql.Connection con2 = null;

编辑:更正，实际上是远远不够的，您将遇到相同的问题，因为您的getConnection2Url方法也不是静态的。更好的解决方案可能是改为进行以下更改:

 public static void main (String[] args) {
     new testconnect().run();
 }

 public void run() {
     con2 = java.sql.DriverManager.getConnection(getConnectionUrl2());
 }