Random number generator with no duplicate

I am having a hard time trying to ensure no duplicates numbers appear in the following code below. I tried to create an ArrayList to add all the possible index of the array and then gradually remove the values of the array from the List as more elements are generated by the number generator. This; however, didnt work as I expected. I've been trying to think about it but Haven't been able to come up with a viable solution.

Random randGen = new Random();
public boolean onTouchEvent(MotionEvent touchevent) {

switch (touchevent.getAction()) {
    case MotionEvent.ACTION_DOWN: {
        x1 = touchevent.getX();
        y1 = touchevent.getY();
        break;
    }
    case MotionEvent.ACTION_UP: {
        x2 = touchevent.getX();
        y2 = touchevent.getY();


        int maxLength=exampleArray.length;
        List<Integer>indices=new ArrayList<Integer>(maxLength);
        for(int i=0;i<maxLength;i++){
            indices.add(i);
        }

        int randomApple = randGen.nextInt(exampleArray.length);
        int randomNum=indices.get(randomApple)  ;
        indices.remove(randomApple);
        textView.setText(exampleArray[randomNum]);

        if (x1 < x2) {

        }

        if (x1 > x2) {

            //textView.setText(exampleArray[randomNum]);

        }

    }
    }

    return false;
}