Java – why do I use random run to get the same number?

I'm 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 the output of this book, namely:

j : 59
k : 56

If I use

Random rand = new Random();

No 47 random class generates random numbers, it doesn't matter, but why if I put the number 47 into J = Rand nextInt(100)1; Why do I get the same book output? thank you

Solution

From documentation:

You can specify the seed in the constructor

You can also see: pseudorandom number generator – Wikipedia