How to fix RuntimeException?

Question

import java.sql.Connection;

public static void main(String[] args) throws SQLException, RuntimeException {


    try{

           DriverManager.registerDriver(new com.mysql.cj.jdbc.Driver());
                       
   String connectionURL="jdbc:mysql://localhost:3306/aaa?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC";
  String login="root";
  String password="aaa";
        
        
        try (Connection conn = DriverManager.getConnection(connectionURL, login, password)) {
            Statement stmt = conn.createStatement();
            
            
            ResultSet rs = stmt.executeQuery("SELECT * FROM Lista1");
            
            
            while(rs.next()) {
                System.out.println(rs.getString("nazwa"));
            }
            rs.close();
            
            
            stmt.close();
        }
    }
    
    catch(SQLException e) {
         System.out.println("Blad polaczenia:");
          e.printStackTrace();
    }
    
    catch(RuntimeException e) {
         System.out.println("Blad polaczenia:");
          e.printStackTrace();
    }

The console log throws:

    Exception in thread "main" java.lang.RuntimeException: 
at cccc.web.Main.main(Main.java:1)

I tried to delete return, but it still threw bad issue. I tried many things but I don't know how to fix it. I don't know how to solve it. And I spent many many many times to fight with it!!!!

You can't. You need to find the more specific reason for the exception's being thrown. Where is the rest of the exception's stack trace information? — Hovercraft Full Of Eels, Sep 22 '20 at 23:18
You cannot have methods outside of classes. `RuntimeException` in **line 1** likely means that the actual error is a compilation error, because the **source file did not compile**. — Andreas, Sep 22 '20 at 23:54

score 1 · Answer 1 · answered Sep 22 '20 at 23:48

The exception object contains two things that tell you what happened: the specific type of the exception (RuntimeException is a base), and if you're lucky, a text message telling you what the problem is.

Print them in your exception handler.

    System.out.println("Exception: " + e)

And, of course, the stacktrace tells you the exact line of your source file that caused the problem.

This is not really a matter of 'fixing' an exception, it's a matter of understanding what is going on and writing code to handle that situation.

score 0 · Answer 2 · answered Sep 22 '20 at 23:46

When an error tells you that the exception happened on the first line, that very much looks like a parsing issue. Take a look here:

    try (Connection conn = DriverManager.getConnection(connectionURL, login, password)) {
        Statement stmt = conn.createStatement();
        
        
        ResultSet rs = stmt.executeQuery("SELECT * FROM Lista1");
        
        
        while(rs.next()) {
            System.out.println(rs.getString("nazwa"));
        }
        rs.close();
        
        
        stmt.close();
    }

The code above is a try without a catch. It's inside an outer try. But once you are using a try, you need a catch. Fix this parsing error and let's see whether there are other problems as well.

How to fix RuntimeException?

2 Answers2