I will post my question at the bottom.
Below is the class that other classes extend from.
public class people {
class family extends people {
}
class friends extends people {
}
class coworkers extends people {
}
}
Below is the class that has the method getAllPeopleByClass that gets invoked by the getMembers() method in the selection classes:
public class processing {
static processing process = null;
private Collection<family> familyList = new ArrayList<family>();
private Collection<coworkers> cowList = new ArrayList<coworkers>();
private Collection<friends> friendList = new ArrayList<friends>();
public processing(){
}
public static processing getInstance() {
if (process == null)
process = new processing();
return process;
}
public <T> Collection<people> getAllPeopleByClass(Class<T> clazz) {
Collection<people> peopleCollection;
peopleCollection.addAll(getList(clazz));
return peopleCollection;
}
private <T> Collection<? extends people> getList(Class<T> clazz) {
if (clazz == family.class) {
return familyList;
} else if (clazz == coworkers.class) {
return cowList;
} else { // else if clazz == friends.class
return friendList;
}
}
And finally, the classes that use processing:
public class familySelection {
public Collection<family> getMembers() {
Collection<family> f;
f = processing.getInstance().getAllPeopleByClass(family.class); //type mismatch
return f;
}
}
public class coworkerSelection {
public Collection<coworkers> getMembers() {
Collection<coworkers> c;
c = processing.getInstance().getAllPeopleByClass(coworkers.class); //type mismatch
return c;
}
}
public class friendsSelection {
public Collection<friends> getMembers() {
Collection<friends> f;
f = processing.getInstance().getAllPeopleByClass(friends.class); //type mismatch
return f;
}
}
My problem is that I get type mismatch from the getAllPeopleByClass call in each of my getMembers() methods.
I have tried this:
public class familySelection {
public Collection<family> getMembers() {
Collection<? extends people> f; //changed to extend from people
f = processing.getInstance().getAllPeopleByClass(family.class);
return (Collection<family>) f; //cast warning - dont want that
}
}
This works, but I get a cast warning, which I don't want and I don't want to suppress it. This is the closest I have come to fixing the problem. Also, the return type of getMembers() must remain as is. Does anyone have a way to do this without any warnings? Or even somehow handle this generically? Thanks!
public <T> Collection<T> getAllPeopleByClass(Class<T> clazz) {
Collection<T> peopleCollection = new ArrayList<T>();
for(people p : getList(clazz)) {
peopleCollection.add(clazz.cast(p));
}
return peopleCollection;
}