Creating an array of Sets in Java

Question

I\'m new to Java so I\'m probably doing something wrong here, I want to create an array of Sets and I get an error (from Eclipse). I have a class:

public class R         


        

Answer 1

You might want to consider using Guava's Multimap where the key is the index. This will handle creating the Sets for each index as you need them.

SetMultimap

SetMultimap<Integer, Recipient> groupMembers;

Answer 2

From http://www.ibm.com/developerworks/java/library/j-jtp01255/index.html:

you cannot instantiate an array of a generic type (new List<String>[3] is illegal), unless the type argument is an unbounded wildcard (new List<?>[3] is legal).

Rather than using an array, you can use an ArrayList:

List<Set<Recipient>> groupMembers = new ArrayList<Set<Recipient>>();

The code above creates an empty ArrayList of Set<Recipient> objects. You would still have to instantiate every Set<Recipient> object that you put into the ArrayList.

Answer 3

Arrays don't support Generics. Use an ArrayList:

ArrayList<Set<Recipient>> groupMembers = new ArrayList<Set<Recipient>>();