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Java: generating random number in a range

I need a little help.

What code would I use to create a random number that is 5 digits long and starts with either 1 or 2?

In order to use as a company employees ID?

Answer 1

Depending on how you approach the problem something like that:

public int gen() {
    Random r = new Random( System.currentTimeMillis() );
    return 10000 + r.nextInt(20000);
}

Or something like that (you probably want the instantation of the Random object of of the method but I just put it here for simplicity) :

public int gen() {
    Random r = new Random( System.currentTimeMillis() );
    return ((1 + r.nextInt(2)) * 10000 + r.nextInt(10000));
}

The idea is that 1 + nextInt(2) shall always give 1 or 2. You then multiply it by 10000 to satisfy your requirement and then add a number between [0..9999].

Here’s are some example output:

14499
12713
14192
13381
14501
24695
18802
25942
21558
26100
29350
23976
29045
16170
23200
23098
20465
23284
16035
18628