线程“AWT-EventQueue-0”中的异常java.lang.NullPointerException

Question

我的代码停止工作，发生了这种错误

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at ultimate_library.unified.showAll(unified.java:47) at ultimate_library.unified.<init>(unified.java:34) at ultimate_library.unified$8.run(unified.java:653)

下面的代码没有任何错误，我只是不明白它是否工作，但有时它工作但它发送此错误“java.sql.SQLTransactionRollbackException：在请求的时间内无法获得锁”

public unified() {
    initComponents();
    DoConnect();        
    showAll();
    DoConnect2();        
    showAll2();
}

void showAll(){
   try{
   rss = stmt.executeQuery("SELECT * FROM accounts");
   while(rss.next())
   {
       String name = rss.getString("name");
       String email = rss.getString("email");
       String bdays = rss.getString("bday");
       loginModel.addRow(new Object[]{name, email, bdays});
   }
   }catch(SQLException err){
        System.out.println(err);
   }
}

public static void main(String args[]) {

    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new unified().setVisible(true);
        }
    });
}

Answer 1

我发现了我的错误，而不是rss，我将其替换为rs2。

void showAll(){
   try{
   rs2 = stmt.executeQuery("SELECT * FROM accounts");
   while(rs2.next())
   {
       String named = rs2.getString("name");
       String emailss = rs2.getString("email");
       String bdayss = rs2.getString("birthday");
       loginModel.addRow(new Object[]{named, emailss, bdayss});
   }
   }catch(SQLException err){
        System.out.println(err);
   }
}