Generate random number without repetition java

if (max < numbersNeeded)


{


    throw new IllegalArgumentException("Can't ask for more numbers than are available");


}


Random rng = new Random(); // Ideally just create one instance globally


// Note: use LinkedHashSet to maintain insertion order


Set generated = new LinkedHashSet();


while (generated.size() < numbersNeeded)


{


    Integer next = rng.nextInt(max) + 1;


    // As we're adding to a set, this will automatically do a containment check


    generated.add(next);


}

Also Watch this video

How to Generate Random Numbers in Javascript Without Repetitions