How do we generate a random but unique number in Java

Question

I am trying to generate a random unique number for every Http request hitting my application.

How do make sure the uniqueness of such a number. Does java provide any method or API for this?

If it's random, it's not guaranteed to be unique. Look for Unique ID solutions, not random ones. — Denys Séguret, Apr 09 '13 at 08:31
Take a look at the [UUID](http://docs.oracle.com/javase/6/docs/api/java/util/UUID.html) class. — Perception, Apr 09 '13 at 08:32
Check this: http://stackoverflow.com/questions/8115722/generating-unique-random-numbers-in-java — G.S, Apr 09 '13 at 08:36

score 4 · Answer 1 · answered Apr 09 '13 at 08:33

4

You could use the java.util.UUID class for that.

UUID rand = UUID.randomUUID();
System.out.println(rand);

answered Apr 09 '13 at 08:33

Rahul

score 2 · Accepted Answer · answered Apr 09 '13 at 08:36

2

answered Apr 09 '13 at 08:36

rvini

4

Doesn't really make any attempt to create *unique* numbers, though... – Henrik Aasted Sørensen Apr 09 '13 at 08:40

2 Answers2