Java Random - how to keep the value?

Completely stuck with Java Random. Digging whole bunch of info but can not solve this. I need to generate new random values of randomWidth and randomHeight only at the beginning and after drawBitmap becomes false again. But as you can see here I generate new random values each time I am loopping. How to keep once generated randomWidth and randomHeight until: drawBitmap = false; startTime = System.currentTimeMillis(); ??

long startTime;
boolean drawBitmap;
//
Random rnd = new Random();

        randomWidth = rnd.nextInt((100 - 10) + 100);
        randomHeight = rnd.nextInt((200 - 10) + 200);       
//


while (true) {

if (System.currentTimeMillis() - startTime >=5000) {
            drawBitmap = true;

        }

        if (System.currentTimeMillis() - startTime >= 10000) {
            drawBitmap = false;
            startTime = System.currentTimeMillis();
        }   

        if (drawBitmap) {
            canvas.drawBitmap(chooseRandomBitmap(map), randomWidth, randomHeight, p);
        }
}