JCheckbox change the text position

jCheckBox.setHorizontalTextPosition(SwingConstants.LEFT);

It's actually inherited from AbstractButton, but you can find this also for JLabels (in this case, it's relative to the icon you may use in the label).

Now this is assuming you want just a particular change on this one component. If your goal is to reverse the direction of all components in your application (for example for a right to left reading), you should probably look into component orientation, with the setComponentOrientation and applyComponentOrientation methods.