How to convert Set<String> to String[]?
Use the Set#toArray(IntFunction<T[]>)
method taking an IntFunction
as generator.
String[] GPXFILES1 = myset.toArray(String[]::new);
If you're not on Java 11 yet, then use the Set#toArray(T[])
method taking a typed array argument of the same size.
String[] GPXFILES1 = myset.toArray(new String[myset.size()]);
While still not on Java 11, and you can't guarantee that myset
is unmodifiable at the moment of conversion to array, then better specify an empty typed array.
String[] GPXFILES1 = myset.toArray(new String[0]);
Java 11
The new default toArray
method in Collection
interface allows the elements of the collection to be transferred to a newly created array of the desired runtime type. It takes IntFunction<T[]> generator
as argument and can be used as:
String[] array = set.toArray(String[]::new);
There is already a similar method Collection.toArray(T[])
and this addition means we no longer be able to pass null
as argument because in that case reference to the method would be ambiguous. But it is still okay since both methods throw a NPE anyways.
Java 8
In Java 8 we can use streams API:
String[] array = set.stream().toArray(String[]::new);
We can also make use of the overloaded version of toArray() which takes IntFunction<A[]> generator
as:
String[] array = set.stream().toArray(n -> new String[n]);
The purpose of the generator function here is to take an integer (size of desired array) and produce an array of desired size. I personally prefer the former approach using method reference than the later one using lambda expression.
Use toArray(T[] a) method:
String[] array = set.toArray(new String[0]);