[java] Java: Difference between the setPreferredSize() and setSize() methods in components

What is the main difference between setSize() and setPreferredSize(). Sometimes I used setSize(), sometimes setPreferredSize(), sometimes one does what I want, sometimes the other.

What call should I use for JFrames and JPanels?

setSize will resize the component to the specified size.

setPreferredSize sets the preferred size. The component may not actually be this size depending on the size of the container it's in, or if the user re-sized the component manually.

setSize() or setBounds() can be used when no layout manager is being used.

However, if you are using a layout manager you can provide hints to the layout manager using the setXXXSize() methods like setPreferredSize() and setMinimumSize() etc.

And be sure that the component's container uses a layout manager that respects the requested size. The FlowLayout, GridBagLayout, and SpringLayout managers use the component's preferred size (the latter two depending on the constraints you set), but BorderLayout and GridLayout usually don't.If you specify new size hints for a component that's already visible, you need to invoke the revalidate method on it to make sure that its containment hierarchy is laid out again. Then invoke the repaint method.

IIRC ...

setSize sets the size of the component.

setPreferredSize sets the preferred size. The Layoutmanager will try to arrange that much space for your component.

It depends on whether you're using a layout manager or not ...