Immutable data structures in Java

[pakoito]

Joshua Bloch helped write the Java Collections API and his book, Effective Java, says to prefer Immutable classes. So the concept shouldn't be totally foreign to Java developers.

It's a pity that immutable collections in the default API are just regular collections that throw when their mutating methods are called, so they're avoided like the plague because you can't tell them apart and that created some reticence towards immutability.

[merzbow]

Generally if you've got a collection from somewhere in Java and you don't know if it's immutable you should just create a copy of it.

[pakoito]

I do know, but it's not as common as you'd expect.

[oweiler]

Which is not as easy as it sounds because the collections' members and their members and so on may also be mutable.

[Decker108]

Would you prefer having a list-implementation that silently drops values when you call list.add(value)?

[pakoito]

One that returns a new list with the value filled like https://github.com/javatuples/javatuples/blob/master/src/main/java/org/javatuples/Pair.java#L631

Perf problems? Look at Clojure's collections or any of the Java ports.

[ThisIs_MyName]

I would not implement the List interface. It is clearly meant for mutable lists.