Creating an Array of Sets in Java
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...
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 Recipient
{
String name;
String phoneNumber;
public Recipient(String nameToSet, String phoneNumberToSet)
{
name = nameToSet;
phoneNumber = phoneNumberToSet;
}
void setName(String nameToSet)
{
name = nameToSet;
}
void setPhoneNumber(String phoneNumberToSet)
{
phoneNumber = phoneNumberToSet;
}
String getName()
{
return name;
}
String getPhoneNumber()
{
return phoneNumber;
}
}
and I'm trying to create an array:
Set<Recipient>[] groupMembers = new TreeSet<Recipient>[100];
The error I get is "Cannot create a generic array of TreeSet"
What is wrong ?
3 Answers
From :
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.
Arrays don't support Generics. Use an ArrayList:
ArrayList<Set<Recipient>> groupMembers = new ArrayList<Set<Recipient>>();
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<Integer, Recipient> groupMembers;
Maya is a hardware enthusiast who tests and reviews smart home devices, smartphones, wearables, and audio gear. She focuses on practical consumer value and build quality.
