用Java生成随机Long值

Question

I am trying to generate two 9 digit long random long value in Java using the below code:

for (int i =0;i<2;i++) {                
    String axisIdStr = Long.toString((long)(System.nanoTime() * (Math.random() * 1000)));
    System.out.println("@@@@@@@@ axisIdStr "+axisIdStr);
    String axId = axisIdStr.substring((axisIdStr.length() -9), axisIdStr.length()) ;
}

But when I run this in windows, i get two different numbers where as when run in mac, I get same two numbers. Why is this happening ? Can you suggest a better way to generate the long values?

Answer 1

According to your requirement you need to generate 9 digit random numbers. As in the comment suggested you can do it using random.Below I have just given one solution to generate random number between two numbers.

long lowerLimit = 123456712L;
long upperLimit = 234567892L;
Random r = new Random();
long number = lowerLimit+((long)(r.nextDouble()*(upperLimit-lowerLimit)));

Answer 2

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You could create an array a[] of int of size 9, and populate with random integers 0-9. Then sum the array up multiplying accordingly.

a[8]*1 + a[7]*10 + a[6]*100 ...

You need to make sure that a[0] only takes digits 1-9 tho...

To get even more random sequence, you Ideally should work on Strings, then you would be able to get 0 on the start position of your random "string", it won't be a number.

Or maybe generate somthing pseudo random and strip last 9 digits out of it.

That's the DIY version of what you could accomplish with what's already out there...

Regards