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Asked: 2026-05-28T04:43:23+00:00

I am learning Java (slowly) from the ground up, but every now and again

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I am learning Java (slowly) from the ground up, but every now and again I peak at some “real” code and I found something that confused me.

The following line and ones like it: 

JPanel panel = (JPanel) container.getContentPane();

My question is what is happening between (JPanel) and container.getContentPane()? Its not like they are being multiplied right?

I know this is a basic part of the language and as I continue learning I’ll get to this part, but I got really curious and wanted to know what it was right away. I didn’t really know what to google to get the answer.

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1 Answer

  1. Editorial Team

    Its not like they are being multiplied right?

    No. It means “get this thing and treat it as a JPanel.” It’s called type casting and that syntax is used in C++, C# and many other languages.

    You have to make sure that the way that the classes are related to each other allows for casting. For example, this wouldn’t work:

    JPanel p = new JPanel();
JComponent c = (JComponent)p;
JButton b = (JButton)c;

    JPanel is a JComponent and so is JButton, but JButton does not descend from JPanel thus you cannot cast between these objects. You can also cast from a child back to a parent, such as from JSpinner.DefaultEditor back to JPanel, but not from JPanel to JSpinner.DefaultEditor.

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