eclipse報(bào)An error has occurred,See error log for more details. java.lang.NullPointerException，我在網(wǎng)上查了一推資料還是沒解決問題，各位大神有高見？下面是我的代碼：UserInfoDao.java

package com.main.dao;
//查詢用戶名，密碼。
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 UserInfoDao {
    public void login(char username,char pass) {

         Connection con;
         //驅(qū)動(dòng)程序名
         String driver = "com.mysql.jdbc.Driver";
         //URL指向要訪問的數(shù)據(jù)庫名mydata
         String url = "jdbc:mysql://localhost:3306/peoplepower";
         //MySQL配置時(shí)的用戶名
         String user = "root";
         //MySQL配置時(shí)的密碼
         String password = "123459";
           //遍歷查詢結(jié)果集
                  try {
                      //加載驅(qū)動(dòng)程序
                      Class.forName(driver);
                      //1.getConnection()方法，連接MySQL數(shù)據(jù)庫?。?                      con = DriverManager.getConnection(url,user,password);
                      if(!con.isClosed())
                          System.out.println("Succeeded connecting to the Database!");
                      //2.創(chuàng)建statement類對(duì)象，用來執(zhí)行SQL語句??！
                      Statement statement = con.createStatement();
                      //要執(zhí)行的SQL語句
                      String sql="select * from userinfo where username='"+username+"and password='"+pass+"'";
                      //3.ResultSet類，用來存放獲取的結(jié)果集??！
                      ResultSet rs = statement.executeQuery(sql);
                      System.out.println("-----------------");
                      System.out.println("執(zhí)行結(jié)果如下所示:");  
                      System.out.println("-----------------");  
                      System.out.println("用戶名" + "\t" + "密碼");  
                      System.out.println("-----------------");  
                       
                      String us = null;
                      String psw = null;
                      while(rs.next()){
                          //獲取stuname這列數(shù)據(jù)
                          us = rs.getString("username");
                          //獲取stuid這列數(shù)據(jù)
                          psw = rs.getString("password");
          
                          //輸出結(jié)果
                          System.out.println(us + "\t" + psw);
                      }
                      rs.close();
                      con.close();
                  } catch(ClassNotFoundException e) {   
                      //數(shù)據(jù)庫驅(qū)動(dòng)類異常處理
                      System.out.println("Sorry,can`t find the Driver!");   
                      e.printStackTrace();   
                      } catch(SQLException e) {
                      //數(shù)據(jù)庫連接失敗異常處理
                      e.printStackTrace();  
                      }catch (Exception e) {
                      // TODO: handle exception
                      e.printStackTrace();
                  }finally{
                      System.out.println("數(shù)據(jù)庫數(shù)據(jù)成功獲?。?！");
                  }
    }
    
    public void main(String[] args) {
        UserInfoDao dao=new UserInfoDao();
        dao.login('1', '1');
    }
}

在tomcat上運(yùn)行后出現(xiàn)以下結(jié)果：