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 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 ?

Answer 1

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.