Generate float Random number between [0,1] and restricting decimal

Question

I want to generate Random Float numbers between Interval [0,1]. The generated Random values will be compared with an input from a file. The content of the File is a probability (float values) and hence they are in range[0,1] and it looks like:

0.55

0.14

0.005

0.870

0.98

0

1

I am reading this File and storing probability values into a DoubleList. Now I want to generate a float Random Number between [0,1]. As you see the file have probability values upto 1 digit, 2 digits decimal and 3 digits decimal as well. I am using following Code:

public static double randomNumberGenerator()
{
    double rangeMin = 0.0f;
    double rangeMax = 1.0f;
    Random r = new Random();
    double createdRanNum = rangeMin + (rangeMax - rangeMin) * r.nextDouble();
    return(createdRanNum);
}

The random float value generated should be also be like Probabilities values (like generated upto the maximal decimal digits as in the file). How can I restrict the generated decimal digits?

I checked the following Link: Java random number between 0 and 0.06 . People suggested Int number generation and then did the double division by 100. Is this the good way? Can't we restrict the decimal generated directly?

PS: If I compare the random generated number from the above code with the double values from File, would there be some memory fall issues in the DoubleList?

You need to word your question more clearly. Am I correct that you want to generate a random number, in the range (0,x) where x is the value in the file? For example, for the first number 0.55, you want a random number in the range (0,0.55) ? — James Wierzba, Oct 30 '15 at 14:07
`double createdRanNum = rangeMin + (rangeMax - rangeMin) * r.nextDouble();` is the best solution you will gonna get. There is no way to cheat your way out of this one without having your numbers being only semi-random, by introducing other constraints, which may follow easier logic at the expense of less true variability. — The Law, Oct 30 '15 at 14:09
Hii James, Thanks for your answer. No. I don't want to generate the numbers in the range on the File. I want to generate the random number in the interval [0,1] (both inclusive) but I want to restrict the digits of the random number generated only to three decimal points. Presently I am getting an Output like: 0.1899367620461322 — Shubham agarwal, Oct 30 '15 at 14:10
Hii Law, Thanks for your quick answer. I want to take only upto 3 decimal counts from the generated results by using double createdRanNum = rangeMin + (rangeMax - rangeMin) * r.nextDouble(); How do do this? — Shubham agarwal, Oct 30 '15 at 14:14

score 15 · Accepted Answer · edited Mar 12 '21 at 16:09

15

You could just use Java Random class :

Random rand = new Random();
float f = rand.nextFloat()

which returns the random float number between 0.0f (inclusive) and 1.0f(exclusive).

To round the result of the nextFloat() you could just use an helper method like the following :

public static float round(float d, int decimalPlace) {
    BigDecimal bd = new BigDecimal(Float.toString(d));
    bd = bd.setScale(decimalPlace, BigDecimal.ROUND_HALF_UP);
    return bd.floatValue();
}

edited Mar 12 '21 at 16:09

toto_tata

14,526
27
108
198

answered Oct 30 '15 at 14:08

aleroot

71,077
30
176
213

That's what I wanted to answer first, but OP seems to need to truncate decimals. – Mena Oct 30 '15 at 14:10
@Mena so he can truncate the result of the random next float, I think it is the correct way to go . – aleroot Oct 30 '15 at 14:12
Thanks a lot. Aleroot. I want to truncate the result generated from the double random. How to do that? I don"t want to round off using floor function.. – Shubham agarwal Oct 30 '15 at 14:18
@Shubhamagarwal I've added a round example method to my answer – aleroot Oct 30 '15 at 14:21
Dear Aleroot Thanks for you suggested method. I used it in generating a file but I still see that some elements still have one place after the decimal. Even though it set the paramet of decimalPlace to 3. – Shubham agarwal Oct 31 '15 at 23:17

Generate float Random number between [0,1] and restricting decimal

1 Answers1