You could use e.g. r.nextInt(101)
For a more generic “in between two numbers” use:
Random r = new Random();
int low = 10;
int high = 100;
int result = r.nextInt(high-low) + low;
This gives you a random number in between 10 (inclusive) and 100 (exclusive)
Assuming the upper is the upper bound and lower is the lower bound, then you can make a random number, r, between the two bounds with:
int r = (int) (Math.random() * (upper – lower)) + lower;