CAPSLOCK Correction button

If I accidentally have capslock on it would be nice if I could have a small button that shows up alerting me of the caps lock and an optional button to correct the text. Here's some pseudocode sort of.

if( CAPSLOCK ) //event based if(), idk how to do/write them
{
    String text = user.getCurrentMessage() ;
    user.setCurrentMessage( text.charAt(0) + (text.substring( 1, text.length()).toLowerCase()  )