How Java random generator works?

Question

I wrote program that simulates dice roll

    Random r = new Random();
    int result = r.nextInt(6);
    System.out.println(result);

I want

Answer 1

They're pseudorandom numbers, meaning that for general intents and purposes, they're random enough. However they are deterministic and entirely dependent on the seed. The following code will print out the same 10 numbers twice.

Random rnd = new Random(1234);
for(int i = 0;i < 10; i++)
    System.out.println(rnd.nextInt(100));

rnd = new Random(1234);
for(int i = 0;i < 10; i++)
    System.out.println(rnd.nextInt(100));

If you can choose the seed, you can precalculate the numbers first, then reset the generator with the same seed and you'll know in advance what numbers come out.