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Java

Greg Kitchin
Greg Kitchin
31,522 Points
Posted by Greg Kitchin
Greg Kitchin
31,522 Points

Lists vs Sets

So I'm rereading some notes for a Java exam next week, and I'm gotten to sets and lists, and I'm trying to see what advantage one has over the other. So far,

Lists are indexed, they can grow and shrink as needed, and they allow duplication.

Sets on the other hand, can also grow and shrink as needed, do not allow duplication, and are not indexed (any item has to be found by looping through it).

So I'm not seeing much that sets have over lists. Lists are easier to find the items required, allow duplication, and seem to offer far more control to the end user. Why would you use a set over a list? The only possible issue I can see is making sure duplication isn't possible, and even then, could probably be resolved with testing for conditions or such (for example, I wrote a tarot deck simulator program that would randomly generate 3 different numbers to represent each card, but duplication is possible. Using a set, I could get round that issue probably.)

1 Answer

Zuhayr Elahi
Zuhayr Elahi
2,582 Points

Hello. So this is really an interesting question. Although Lists are easier to implement and seem like they might be better, sometimes a Set is needed.

Lets start with an example. You have a table of ip address. e.g. (12.134.567.12, 45.134.23.56.78). Now IP addresses have to be unique. So you and I cannot be on the same network and have the same ip address. TO ensure that there are no duplicate ip addresses it would be better to store them in a Set. A Set allows us to ensure the user does not enter duplicates themselves.