[Ljava.lang.Object; cannot be cast to [Ljava.lang.String; [duplicate]

Question

The following code (run in netbeans) always gives me a ClassCastException in the last line:

private void GetModules() throws SQLException {
    stm = conn.prepareStatement("SELECT * FROM module");
    Rs = stm.executeQuery();
    Lliste.clear();
    modules.clear();
    while (Rs.next()) {
        String[] str_l = new String[5];
        for (int i = 0; i < 5; i++)
            str_l[i] = Rs.getString(i + 1);
        Lliste.add(str_l);
        modules.add(str_l[1]);
    }
    stm.close();
    Rs.close();
    liste.setListData((String[]) modules.toArray());
}

when I run the code, I get the following Error:

    Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Ljava.lang.String;

I tried also to not cast it but it gives me an error. Could someone please help me? I'm really confused with this!

Not related to the problem, but you probably shouldn't be running this piece of code from the EDT. — Renatols
– Renatols, Commented May 4, 2018 at 16:35

davidxxx · Accepted Answer · 2018-05-04 16:31:25Z

0

Use the overloaded List.toArray() method that specifies the return type of the array :

public <T> T[] toArray(T[] a)

In this way :

liste.setListData(modules.toArray(new String[modules.size()]);

answered May 4, 2018 at 16:31

davidxxx

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1 Comment

Paweł Sosnowski Over a year ago

idk why downvoted, reply seems correct, I would only add that you should use empty array as argument for initialization: list.toArray(new String[0]); see more: stackoverflow.com/a/53285440/4270929

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