javafor-loopcollectionsuniqueidentification

Java generate a unique id from an unordered set/list of objects / values

Following is the scanerio.

  1. How can we generate a unique id (string/number), from a given unordered collection/set of objects (having their own uids).

  2. How to make sure the generated id will always be the same even if the order of the objects changes in the collection/set.

I am working with groups of objects and each group needs a uid, to represent certain objects are present in it regardless of the order of the object, hope it makes sence, thanks in advance for your help.

Solution

  • Given that the number of possible objects are so limited, you can easily do this. Give each object a value which is a power of 2 (1,2,4,8,16, etc.) Then, for the collection, just sum the values of the objects in the collection. The result should fit in a 32 bit integer.