How to generate 14-digit positive number?

Question

How to generate 14-digit positive number?

Java

Nikki asked July 9th 19 at 11:20

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More answers about "How to generate 14-digit positive number?"

4 answers

Nikki answered on July 9th 19 at 11:26

thank you. both options are good.

merle.Powlowski answered on July 9th 19 at 11:28

Here's another option:

ThreadLocalRandom.current().nextLong(10000000000000L, 100000000000000L);

darron.Wunsch answered on · Accepted Answer · 2019-07-09T11:22:28.105Z

darron.Wunsch answered on July 9th 19 at 11:22

Solution

If you need a long (say 100 digits), so it can be costly (for example, the 14 digit):

BigInteger b;
do{
 b = new BigInteger(48, new SecureRandom());
} while (b.toString().length()!=14);
System.out.println(b.toString());

Why so difficult? To generate 7 two-digit, and assemble into 14-digit. - nicklaus commented on July 9th 19 at 11:25

:
1) And if you need 500 digits? Then just change the 48 to a different value.
2) int allows you to generate a 19 digit (if the least significant 63 bits).
For the 14 digit enough

long l =10000000000000L +(long)(Math.random()*90000000000000L);

- darron.Wunsch commented on July 9th 19 at 11:28

Marat, your algorithm with a while loop has an unknown execution time. And this is not good. The second option - norm, Yes. - nicklaus commented on July 9th 19 at 11:31

If you generate really large values easier to take Random and fill a byte array of the necessary size and make it to a BigInteger. If the number of bits is not a multiple of 8, additionally you need to apply a mask to the first byte. - charity84 commented on July 9th 19 at 11:34

It turns out even BigInteger has a constructor like this - charity84 commented on July 9th 19 at 11:37

: so I did and used :) - darron.Wunsch commented on July 9th 19 at 11:40

: oops, think a little)) - charity84 commented on July 9th 19 at 11:43

Kylie_Bergstr answered on · Accepted Answer · 2019-07-09T11:24:28.105Z

Kylie_Bergstr answered on July 9th 19 at 11:24

Solution

Now, seems right and works fast... it's faster, well, that is)

public static BigInteger generateBigInteger(int length, Random random) {
 StringBuilder builder = new StringBuilder(length);
 builder.append(random.nextInt(9) + 1);
 for (int i = 1; i < length; i++) {
builder.append(random.nextInt(10));
}
 return new BigInteger(builder.toString());
 }

Upd: the solution above in the comments better :D