Java random numbers, must be in ascending order and no repetition [on hold]

I need to generate 20 random numbers from the range 1-100. No repetition. Must be in ascending order. Anyone knows how to do this coding?

So far I have:

System.out.println ("Generate 20 unique numbers between 0 - 100"); 
Random randomGenerator = new Random(); 
for (int idx=1; idx<=20; ++idx) {
  System.out.println(randomGenerator.nextInt(100)); 
}  int randomInt = randomGenerator.nextInt(100);
        System.out.println("unique number :" +randomInt);
    }
    System.out.println("Generated");