Set concept in Java of Collection

[Dinesh Tahiliani]

Hello,

Which method Set use for not allowing duplicates ? Please explain with example

[Lucas Smith]

equals() method and hashCode() if it is HashSet.
Correct me if I am wrong.

[Jason Irwin]

[pedantic]Set doesn't use any methods, it's just an interface[/pedantic]

Lukas is right and that's why if you override equals or hashCode, you should really override the other one as well. If you don't, you can get some very, very strange behaviour in your sets (and maps). Like being able to add something to a set or map, but never able to find out later on if it is in there.

You appear to have Sierra&Bates - read chapter 7 (Objective 6.2), it's excellent.

[Dinesh Tahiliani]

You mean to say that set uses equals() mtd to compare the object and doesn't allow duplicates?

[Jason Irwin]

Exactly how a set decides it has a duplicate or not depends on what type of set you are talking about.

Hashed sets (HashSet, LinkedHashSet etc) will use hashCode and equals.
Sorted sets (TreeSet etc) does something else (0 on comparison and then an equals test I think; not found good documentation on the specifics and it's not in Sierra&Bates).
CrazyMonkeySet may do something different again.

This is all in Chapter 7.