帮忙看看为什么数据库是连上了还是有

Question

sql exception:java.lang.NullPointerException

package function;
//JDBC中的所有类和接口都在java.sql包下。
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

public class Execute{

private static String driver="oracle.jdbc.OracleDriver";//声明驱动类字符串

//声明数据库连接字符串
private static String url="jdbc:oracle:thin:@localhost:1521:orcl";

private static Connection con=null;//声明数据库连接对象引用
private static Statement stat=null;//声明语句对象引用

//private static PreparedStatement psInsert=null;//声明预编译语句对象引用

static ResultSet rs=null;//声明结果集对象引用

public static Connection getConnection()//得到数据库连接的方法
{

 try   {    
     Class.forName(driver);//加载驱动类  
     con=DriverManager.getConnection(url,"system","abcA1234");//得到连 接    
     return con;
 } 
 catch (SQLException e) {
     e.printStackTrace();
 }
 catch (ClassNotFoundException e) {
     e.printStackTrace();
 } 
 finally {
     if (con != null) {
         try {con.close();
         }
         catch (SQLException e) {
             e.printStackTrace();
         }
     }
 }
 return null;

}
public static boolean executeSQL(String sqlString) {
boolean executeFlag;
try {
stat.execute(sqlString);
executeFlag = true;
} catch (SQLException e) {
executeFlag = false;
System.out.println("sql exception:" + e.getMessage());
}
return executeFlag;
}

public static boolean query(String sqlString) {

 try {
     rs = null;
     //System.out.println(sqlString);
     rs = stat.executeQuery(sqlString);
 } catch (Exception Ex) {
     System.out.println("sql exception:" + Ex);
     return false;
 }
 return true;

}
public static void main(String[] args) {
Connection conn = getConnection();
if (conn != null) {
System.out.println("连接成功");
}
else {
System.out.println("连接失败");
}
}
}

Answer 1

没有连接成功的错误提示是什么