List<JCheckBox> checkboxes = new ArrayList<JCheckBox>();
for( Component comp : panel.getComponents() ) {
if( comp instanceof JCheckBox) checkboxes.add( (JCheckBox)comp );
}
This assumes all of the JCheckBox instances are a direct child of the container panel. If not then you'd need to recursively visit all the containers of panel using the same logic. Now, while you can do this it's typically better to save these references as you created them into a list. Then you can easily iterate over all of the checkboxes without having to do this code above. If you have embedded components it's better to ask the embedded component to perform whatever operation you want over the checkboxes it owns (as opposed to pulling them out of the component through a getter so you can mess them in some way).