Why I obtain the same number with Random Run?

Question

I am following a book and in this code:

    Random rand = new Random(47);
    int i, j, k;
    j = rand.nextInt(100) + 1;
    System.out.println("j : " + j);
    k = rand.nextInt(100) + 1;
    System.out.println("k : " + k);

I have the same number in output of the book, that is:

j : 59
k : 56

If I use

Random rand = new Random();

without 47 Random Class produces random number and it's ok, but why if I put inside the number 47 joined with j = rand.nextInt(100) + 1; Why I obtain the same output of the book? Thank you

Answer 1

From the documentation:

If two instances of Random are created with the same seed, and the same sequence of method calls is made for each, they will generate and return identical sequences of numbers.

You can specify the seed in the constructor

Creates a new random number generator using a single long seed.

See also:
Pseudorandom number generator - Wikipedia