Get specific class objects from HashSet in Java

Questions

I have a public Set<ProjectItem> projectItems = new HashSet<ProjectItem>(); which can contains two types of classes (ProjectItem is a abstract super class for both of them). The classes are Deliverable and Task. I want get all objects of the class Deliverable from the Set. Therefore I write this:

public Set<Deliverable> allDeliverables(){
Set<Deliverable> result = new HashSet<Deliverable>();
for(Iterator<ProjectItem> iter = projectItems.iterator(); iter.hasNext(); iter.next()){
    if (iter.next().getClass() == Deliverable.class){
    Deliverable del = (Deliverable) iter.next();
    result.add(del);
    }
}
return result;
}

But this makes an exception -

Exception in thread "main" java.lang.ClassCastException: edu.Chryb.ProjectManagement.Task cannot be cast to edu.Chryb.ProjectManagement.Deliverable

in the Line with: Deliverable del = (Deliverable) iter.next();

Is something in the if query wrong?

Thanks for every help.

Answers

Your code is a bit out. Try:

for(Iterator<ProjectItem> iter = projectItems.iterator(); iter.hasNext(); iter.next()){
    ProjectItem item = iter.next();
    if (item.getClass() == Deliverable.class){
        result.add((Deliverable)item);
    }
}

Source

License : cc by-sa 3.0

http://stackoverflow.com/questions/16863655/get-specific-class-objects-from-hashset-in-java

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