final RadioButton[] buttons = {radio_books,radio_games,radio_dvds,radio_electronics};
for (RadioButton this_button : buttons) {
     this_button.setOnClickListener(new OnClickListener() {
     	@Override
     	public void onClick(View v) {
     		for (RadioButton button : buttons) {
     			if ((RadioButton)v != button) {
     				button.setChecked(false);
     			}
     		}
     	}
     });
}