Initialize variable error Java

Question

I am attempting to print some results from an SQL statement inside of Java and I am receiving an error saying these variables need to be initialized but I'm not sure how to go about doing this other than setting them to null which isn't what I want to do here, my error is when attempting to close st, rs and con, I am prompted to initialize the variables but this just sets them to null, here is my code so far:

public static void copyFolder(File src, File dest)
    throws IOException {
    Connection con;
    Statement st;
    ResultSet rs;

    try {
        con = DriverManager.getConnection("removed as it houses sensitive data");
        st = con.createStatement();
        String s = "SELECT Code FROM dbo.\"FK Facades$Dimension Value\" WHERE [Dimension Code] = 'PROJECT'";
        rs = st.executeQuery(s);
        while (rs.next()) {
            rs.getString(1);
            System.out.print(rs);
        }
    } catch (Exception e) {
        System.out.println("No connectarino");
    } finally {
        try {
            st.close();
            rs.close();
            con.close();
        } catch (Exception e) {
            System.out.println("No");
        }
    }
}

Consider using try-with-resources to manage connection, statements and result sets — Vladimir Vagaytsev
– Vladimir Vagaytsev, Commented Jun 28, 2016 at 13:37

Axel · Accepted Answer · 2016-06-28 13:40:55Z

2

In addition to what is already said, you should start using try-with-resources like this:

    try (Connection con = DriverManager.getConnection("removed as it houses sensitive data");
         Statement st = con.createStatement();
         ResultSet rs = st.executeQuery("...")) {
        // your code here
    }

This automatically closes the instances for you, and even gets the corner cases (i.e. exception in close()) right.

answered Jun 28, 2016 at 13:40

Axel

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1 Comment

David Thomlinson Over a year ago

Thank you very much, I have implemented this into my code with the relevant changes and I am now receiving no errors, still won't connect to the database which could be for a totally different reason but thanks once again for solving this issue!

Nicolas Filotto · Accepted Answer · 2016-06-28 13:35:52Z

1

You need to initialize con, st and rs because if for example the first line in the try block fails, you will have no values for these variables so it cannot execute the finally block that is the reason why you get this compilation failure.

So it should be:

Connection con = null;
Statement st = null;
ResultSet rs = null;

...
try {
    if (rs != null)
        rs.close();
    if (st != null) 
        st.close();
    if (con != null)
        con.close();
} catch (Exception e) {
    System.out.println("No");
}

NB: Close the result set before the statement

answered Jun 28, 2016 at 13:35

Nicolas Filotto

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3 Comments

David Thomlinson Over a year ago

Yes I did try to set each variable to null without much luck, will try the other part of the statement now, thanks

Nicolas Filotto Over a year ago

I tested on my side, I don't have any compilation error anymore with what I propose in my answer

David Thomlinson Over a year ago

I attempted to implement your suggestion but it was causing my other errors further down in my code with else statements, I've now fixed this using the first answer using try-with-resources, thanks for your help though!

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