CODEWITHSUNDEEP
javarandombigintegerlargenumber
Jeel Shah
Jeel Shah

Reputation: 3334

Generating very large random numbers java

How can we generate very large random number in java? I am talking something like 10000 digits? I know we have to use BigInteger but how can we do this? What is the most efficent way of doing something like this? Please provide a small example. Thank you.

Upvotes: 13

Views: 14730

Answers (3)

Tefoo
Tefoo

Reputation: 1

You can just type:

int number = (int)(Math.random() * 100);

Also, you can generate even bigger numbers if you change the multiplier:

int number = (int)(Math.random() * 1000);

P.S. You don't need to import a class.

Upvotes: -3

Jaco Van Niekerk
Jaco Van Niekerk

Reputation: 4182

Well, one way is to go to Random.org and download a one of the binary random files. The files are generated from atmospheric noise, so it's very random. I used it for Zobrist keys in my chess engine.

Alternatively you could go

BigInteger b = new BigInteger(256, new Random());

which will give you what you want. In this example, a BigInteger consisting of 256 bits.

Upvotes: 23

Vlad
Vlad

Reputation: 18633

Combine Random.nextBytes(byte[]) with BigInteger(byte[]).

import java.util.*;
import java.math.*;
class Test{
    public static void main(String[]_){

        int n = 16;

        Random r = new Random();
        byte[] b = new byte[n];
        r.nextBytes(b);
        BigInteger i = new BigInteger(b);

        System.out.println(i);
    }
}

Upvotes: 9

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