Java function return value cannot be resolved

mohtasham1983 · 10-25-2007, 02:18 AM

Hello,
This is my first program writing in Java after hello world. I know I have jumped very fast to write a relatively complex program, but I'm not patient enough to learn it step by step by writing simple. However, I m facing a problem when trying to write a function that returns a ResultSet value. When I place the the return statement at the end of function, it says that the variable cannot be resolved and when I place it right after the variable gets initialized, it warns me that the function should return a ResultSet value.

Here is the function:

PHP Code:



public static ResultSet query(String query) 
    { 
           Statement stmt; 
            
           try { 
               Class.forName("com.mysql.jdbc.Driver").newInstance(); 
           } catch (Exception ex) { 
               System.out.println(ex); 
           }   
            
           try { 
               String myUrl = "jdbc:mysql://localhost/University?user=root&password=esteghlal"; 
               Connection conn = DriverManager.getConnection(myUrl); 
               stmt = conn.createStatement(); 
                
               ResultSet rs = stmt.executeQuery(query);  
                
            
             
           } catch (SQLException ex) { 
               System.out.println("SQLException: " + ex.getMessage()); 
              System.out.println("SQLState: " + ex.getSQLState()); 
               System.out.println("VendorError: " + ex.getErrorCode()); 
           } 
           return rs; 
            
    }

As you can see in this example it tells me that rs cannot be resolved. I think this problem is produced by try and catch, but I don't know how to get rid of it.

I will really appreciate your time reading this thread.

Thanks in advance

Nylex · 10-25-2007, 02:39 AM

Try declaring your ResultSet variable outside your try/catch blocks (before you use it, obviously).

mohtasham1983 · 10-25-2007, 02:47 AM

when I declare it right after declaring stmt outside try/catch block, at the end it tells me that The local variable rs may not have been initialized, while it is initialized inside try/catch block.

I have tried different combination of declaring and returning rs in different positions with no success.

Alien_Hominid · 10-25-2007, 07:32 AM

Why not like this:

PHP Code:



public static ResultSet query(String query)
    {
           Statement stmt;
           ResultSet rs;
           
           try {
               Class.forName("com.mysql.jdbc.Driver").newInstance();
           } catch (Exception ex) {
               System.out.println(ex);
               rs = 0;
           }  
           
           try {
               String myUrl = "jdbc:mysql://localhost/University?user=root&password=esteghlal";
               Connection conn = DriverManager.getConnection(myUrl);
               stmt = conn.createStatement();
               
               rs = stmt.executeQuery(query); 
               
           
            
           } catch (SQLException ex) {
               System.out.println("SQLException: " + ex.getMessage());
               System.out.println("SQLState: " + ex.getSQLState());
               System.out.println("VendorError: " + ex.getErrorCode());
               rs = 0;
           } 
           finally { 
               return rs;
           }
    }

Did not check.

mohtasham1983 · 10-25-2007, 10:47 AM

rs cannot be set to zero and finally block does not complete normally.

This error is really strange.

mohtasham1983 · 10-25-2007, 11:08 AM

I got it working. I initialized the rs variable to null when declaring it.

I really appreciate your time.

Thanks

Alien_Hominid · 10-25-2007, 12:11 PM

You can set set rs value to null in catch statements too without declaring it null before them.