How do I turn a Java Enumeration into a Stream?
I have a third party library that gives me an Enumeration<String>. I want to work with that enumeration lazily as a Java 8 Stream, calling things like filter, map and flatMap on it.
Is there an existing library that has this in it? I am already referencing Guava and Apache Commons so if either of those have the solution that would be ideal.
Alternatively, what is the best/easiest way to turn an Enumeration into a Stream while retaining the lazy nature of everything?
Answer
Why not using vanilla Java :
Collections.list(enumeration).stream()...
However as mentionned by @MicahZoltu, the number of items in the enumeration has to be taken into account, as Collections.list will first iterate over the enumeration to copy the elements in an ArrayList. From there the regular stream method can be used. While this is usual for many collection stream operations, if the enumeration is too big (like infinite), this can cause problem because the enumeration has to be transformed in a list then the other approaches described here should be used instead.