Question

I want to display two (or more) JFrames at the same time.
When I close one of them (use the default close button), the other frames should still be visible.

How can I do that?

Answer 1

If you do not want your application to terminate when a JFrame is closed, use

setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE)

instead of

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

From the documentation:

• DO_NOTHING_ON_CLOSE (defined in WindowConstants): Don’t do anything; require the program to handle the operation in the windowClosing method of a registered WindowListener object.
• HIDE_ON_CLOSE (defined in WindowConstants): Automatically hide the frame after invoking any registered WindowListener objects.
• DISPOSE_ON_CLOSE (defined in WindowConstants): Automatically hide and dispose the frame after invoking any registered WindowListener objects.
• EXIT_ON_CLOSE (defined in JFrame): Exit the application using the System exit method. Use this only in applications.

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This was my answer before the question was clarified, might still be useful:

You can use setVisible(false) on your JFrame if you want to display the same frame again.
Otherwise call dispose() to remove all of the native screen resources.