Generating 10 digits unique random number in java

Question

I am trying with below code to generate 10 digits unique random number. As per my req i have to create around 5000 unique numbers(ids). This is not working as expected. It a

Answer 1

this is for random number starting from 1 and 2 (10 digits).

public int gen() {
    Random r = new Random(System.currentTimeMillis());
    return 1000000000 + r.nextInt(2000000000);
}

hopefully it works.