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?

Answer 1

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();
}