[java] Getting Relative Mouse Data

I'm using Java and I need some help getting basic mouse data. Here's the situation: Say I have a 400 x 400 JPanel in the middle of a 500 x 500 JFrame. The JPanel has string drawn to it that prints out the mouse coordinates. If my mouse were placed exactly in the middle of the JFrame, the string should read (200, 200). What is the best way to accomplish this? Thanks!