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This means that when we declare a Set of a particular type, that type will be used to replace all
of the instances of the type variable E in the definition. So by returning a Set<Player> from
getRoster() , we assure that only a Player object can be added to the Set , and the Iterator
that is returned from the iterator() method on that Set will give us only Player objects.
We don't have to cast the result of using the iterator, and the compiler can check all of these
To see how this works in practice, let's go back to our baseball statistics package. We start by
changing the Team interface so that the return value of getRoster() uses generics, adding a
type parameter to the return type:
package org.oreilly.javaGoodParts.examples.statistics;
import java.util.Set;
* The <code>Team</code> interface, which defines
* the notion of a team for our statistics package. A
* team is, at first incarnation, simply a collection of
* players. All teams have a name.
public interface Team {
* Return a <code>String</code> that is the name of
* this team.
String getName();
* Return the players that are on this
* team. The set returned is a set of player
* objects.
Set<Player> getRoster();
* Add a player to the team.
void addPlayer(Player toAdd);
* Remove a player from the team.
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