Java SE (Java Platform, Standard Edition)

Can someone show me a quick example? The JFrame can be empty, I just want to know how to set it's maximum size. I tried using setMaximumSize() and it doesn't work for some reason but setMinimumSize() works fine.

I tried it using a BoxLayout and even using null as a layout manager and can't get it to work. I heard that the other layout managers don't allow you to set the maximum size of a JFrame so that is why I tried it with the layouts that I did.

I tried the following code (imported the necessary classes), but it does not work...

public class MyFrame extends JFrame
{
    public MyFrame()
    {
        super("TestFrame");
        setLayout( new BoxLayout(getContentPane(), BoxLayout.X_AXIS)  );        
        setMaximumSize( new Dimension(400,200)); 
        setSize(300,150);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible( true );                 
    }
    
    
}// end class