CODEWITHSUNDEEP
java
Arun
Arun

Reputation: 338

strategy to create 4 bytes unique Id in java

Our java application has a 4 bytes size restriction to hold unique id.

We are forced to implement a strategy to create unique ids which are 4 bytes in size.

Does any one know a strategy to create it

Upvotes: 2

Views: 1777

Answers (3)

Patashu
Patashu

Reputation: 21773

Yes, start with a random 32 bit integer and increment it.

Anything else will be too demanding as you scale up (e.g. if you have 1 billion already created ids and need to randomly generate a new one, you have to have a 1 billion entry table to check for existence inside... ouch!).

But if it absolutely has to be random and unique, the two strategies you can take are:

1) Have a big HashSet of every id used so far and check for existence in the set whenever you generate a new random ID. If it is, discard and try again.

2) Store all randomly used IDs in the database, and do a SELECT to see if your newly generated random ID exists. If it does, discard and try again.

If the unique ID was larger, you could use a Guid (also known as uuid), which are generated large enough and in such a way that you'll never see two Guids have the same value ever, anywhere, without needing to check.

For Guids/UUIDs in java, see http://docs.oracle.com/javase/7/docs/api/java/util/UUID.html

Upvotes: 5

user2345609
user2345609

Reputation: 1

you can try like this 

private static byte[] synhead = {(byte)0xAA,0x55,0x7E,0x0B};

Upvotes: 0

wangsquirrel
wangsquirrel

Reputation: 135

I think int can meet your demands.

Upvotes: 0

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