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javaclassjcomponent

How to set a class visible from another?

I have a drawing board with some circles, triangles and rectangles. I want to be able to set them visible and not.

The classes name are Circle, Triangle, Rectangle and is extending JComponent, and they all have an unique color.

Someone suggested Triangle c = null; and then use c.setVisible(true) to make it visible - but it only gives Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException referring to c.setVisible(true)

Anyone know a solution to this?

Solution

  • Please use :

    Triangle c = new Triangle();

    c.setVisible(true);

    Instead of null

    Reference variables with null value will always give you NullPointerException when you call it with dot(.) operator.