CODEWITHSUNDEEP
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DroidGalaxy
DroidGalaxy

Reputation: 109

Generate a long random integer in Java

I'm trying to find a way to generate a very big random number. I looked online but couldn't find what I was looking for. I need to generate a random number that is between 1111111111111111111111 and 9999999999999999999999; the number is 22 digits long. If you know how to do it then plz let me know. Thanks

Upvotes: 0

Views: 370

Answers (2)

Milos Lulic
Milos Lulic

Reputation: 627

Here is quick TESTED solution for your needs :

public void generateNumber(){

    BigInteger min = new BigInteger("1111111111111111111111");
    BigInteger max = new BigInteger("9999999999999999999999");

    System.out.println(random(min, max));
}

protected static Random RANDOM = new Random();
public static BigInteger random(BigInteger min, BigInteger max) {
    if(max.compareTo(min) < 0) {
        BigInteger tmp = min;
        min = max;
        max = tmp;
    } else if (max.compareTo(min) == 0) {
        return min;
    }
    max = max.add(BigInteger.ONE);
    BigInteger range = max.subtract(min);
    int length = range.bitLength();
    BigInteger result = new BigInteger(length, RANDOM);
    while(result.compareTo(range) >= 0) {
        result = new BigInteger(length, RANDOM);
    }
    result = result.add(min);
    return result;
}

Upvotes: 2

Babajide Apata
Babajide Apata

Reputation: 693

I have something that I have worked with before

public class RandomString {
private static final Random random = new Random();

public static String numeric(int count) {
    if (count == 0) {
        return "";
    } else if (count < 0) {
        throw new IllegalArgumentException("Requested random string length " + count + " is less than 0.");
    }
    int end = 'z' + 1;
    int start = ' ';
    char[] buffer = new char[count];
    int gap = end - start;
    while (count-- != 0) {
        char ch;
        ch = (char) (random.nextInt(gap) + start);
        if (Character.isDigit(ch)) {
            if (ch >= 56320 && ch <= 57343) {
                if (count == 0) {
                    count++;
                } else {
                    // low surrogate, insert high surrogate after putting it in
                    buffer[count] = ch;
                    count--;
                    buffer[count] = (char) (55296 + random.nextInt(128));
                }
            } else if (ch >= 55296 && ch <= 56191) {
                if (count == 0) {
                    count++;
                } else {
                    // high surrogate, insert low surrogate before putting it in
                    buffer[count] = (char) (56320 + random.nextInt(128));
                    count--;
                    buffer[count] = ch;
                }
            } else if (ch >= 56192 && ch <= 56319) {
                // private high surrogate, no effing clue, so skip it
                count++;
            } else {
                buffer[count] = ch;
            }
        } else {
            count++;
        }
    }
    return new String(buffer);
   }
}

you can call this class like this 

RandomString.numeric(22);

it will do what you want

Upvotes: 0

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