What is the best way to put spaces between objects? Can a Swing JSeparator object be an invisible separator?

Question

I am learning Swing, and finding the behaviour of the JSeparator a bit surprising.

I am trying to put two buttons inside a panel using Swing widgets, inside the NetBeans IDE, my JSeparator "border" property is set to "(No border)" in the properties pane.

Nevertheless a line appears. This is not what I would expect from a separator object. Am I doing something wrong? Coming from a background in Delphi, and C# WinForms, I expect to find some oddities in Swing. But how exactly do you make a transparent gap of a particular size, between two buttons in a panel? Do I have to play with layouts and avoid the JSeparator?

Update: it should be trivial to do this with a layout and without any separator object. So how do you do that? I am looking into the Netbeans layout customizer and properties inspector and finding no way to do it. [the word I am looking for is... Insets. aha.]

Answer: Use Insets, not JSeparator. If you MUST insert something from the palette, use an empty panel. In netbeans, use Customize Layout, and adjust Inset.

Answer 1

JSeparator is meant to be a visible separator between components.

From the javadoc for JSeparator:

JSeparator provides a general purpose component for implementing divider lines - most commonly used as a divider between menu items that breaks them up into logical groupings.

If you want to put a component in between two components that is invisible just use an JPanel instead. Then set the size of the panel with setPreferedSize() and setMin/MaxSize().

Answer 2

Yes, learning to use layouts effectively is going to be the best solution in the long run.

Answer 3

You don't need JSeparator. Most layouts allow you to set gap (space) between compoponents. And Box class can be particularly useful.

Answer 4

You should take a look at the static utility methods on the Box class. They can be used to manufacture fixed struts that act as invisible separators; e.g.

JPanel pnl = new JPanel(new FlowLayout());
pnl.add(new JButton("Hello"));
pnl.add(Box.createHorizontalStrut(10)); // Fixed width invisible separator.
pnl.add(new JButton("Goodbye");

This produces more compact code than creating / configuring a JPanel yourself with appropriate minimum, maximum and preferred dimensions.