Java random number generator

Question

Is it possible to have a user choose the number of digits of a random number, specifically a random Big Integer? For example if the user wants it to be 15 digits long the random number generator would only produce 15 digit long Big Integers.

Solution

You can always generate individual digits of the number randomly. This way for a 15 digit number you can generate 15 digits randomly and then form the number.

Another way:

Lets change the problem to generate random 5 digit number.

Min = 10000
Max = 99999

Now generate a random number between 0 and Max - Min which is 0 and 89999 and add it to Min.

Random = Min + Math.random() * (Max - Min)