Question

From JavaDoc:

public void validate()

Validates this container and all of its subcomponents. Validating a container means laying out its subcomponents.

That is what I want to do. With an as lightweight component as possible. But when I do this whith a JComponent a call to validate() doesn’t make the component "valid".

    JComponent c = new JComponent() {};
    System.out.println(c.isValid()); // false
    c.validate();
    System.out.println(c.isValid()); // false

Why can’t I make a JComponent valid?

Answer 1

In the docs for isValid() it says:

A component is valid when it is correctly sized and positioned within its parent container and all its children are also valid.

This is the case until you reach a Top-Level Container (JFrame, JInternalFrame or JApplet). In the example you have in your question, your JComponent doesn’t have a parent so it can never be valid.