problems with simple roll down menu in java

[Krtek80]

Hello I have a problem withg following error message being popped up after attempting to compile the java code.
Many thanks for any idea which might explain why this is so. Milan.
THE ERROR MESSAGE IS:
C:\Program Files\Java\jdk1.7.0_04\bin>javac GUI10_206.java
Note: GUI10_206.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

the code is:

import java.awt.*;
import javax.swing.*;
public class GUI10_206 {
public static void main(String[] arg) {
Okno okno = new Okno();
}
}
class Okno extends JFrame {
public Okno() {
super("Nadpis Okna");
setSize(400, 100);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
Container kon = getContentPane();
kon.setBackground(Color.green);
FlowLayout srf = new FlowLayout();
kon.setLayout(srf);
JComboBox rseznam1 = new JComboBox();
rseznam1.addItem("Jedna");
rseznam1.addItem("Dva");
rseznam1.addItem("Tri");
kon.add(rseznam1);
setContentPane(kon);
}
}

[Tolls]

Please use [code] tags [/code] when posting code.
Did you do as the message suggested and use the -Xlint:unchecked option on the command line?
That would tell you exactly where that warning (and it's a warning, not an error) is being flagged.

[DarrylBurke]

I'll add a hint: JComboBox was genericized in Java 7. So when tracking down the warning, make sure to refer to the Java 7 API -- not any earlier version.

db

[Krtek80]

I'll add a hint: JComboBox was genericized in Java 7. So when tracking down the warning, make sure to refer to the Java 7 API -- not any earlier version.

db

THANKS FOR YOUR HELP HOWEVER I HAVE VERSION "Java Edition Version 11.1.2.1.0", ANY IDEA WHAT THE PROBLEM COULD BE?
MANY THANKS MILAN.

[Tolls]

No need to shout...
There is not version 11.1.2.1.0 (unless it's Oracles internal database one maybe, but I have no idea how the numbering on that works).
From your first post above it is clear you are using Java 1.7 ("C:\Program Files\Java\jdk1.7.0_04\bin").

Anyway, Darryl has said what the warning is about, which is that JComboBox is now a generic class.
If you don't know about generics, here's the tutorial.

[Krtek80]

No need to shout...
There is not version 11.1.2.1.0 (unless it's Oracles internal database one maybe, but I have no idea how the numbering on that works).
From your first post above it is clear you are using Java 1.7 ("C:\Program Files\Java\jdk1.7.0_04\bin").

Anyway, Darryl has said what the warning is about, which is that JComboBox is now a generic class.
If you don't know about generics, here's the tutorial.

Ok, thanks for your help, I am new to Java....:)