Java获取不在arraylist中的元素

Question

I am trying to add users to a model. I want to add all the users that are in MembersArray but not in membersAvailableArray .

membersAvailableArray = all members in the class.
MembersArray = all members

Im trying to get all members that are in MembersArray but not membersAvailableArray

DefaultListModel<String> model2 = new DefaultListModel<>();

       for(Member allMems: MembersArray)
       {
             for(Member mems: membersAvailableArray)
             {

                 if(!allMems.getUsername().equals(mems.getUsername()))
                 {
                     model2.addElement(allMems.getFirstName() + " " + allMems.getLastName());
                 }


             }
       }
       availableMembersJList.setModel(model2);

Answer 1

You do not need any looping here, just some good old "All" operations:

ArrayList<Member> membersToAdd = members.clone();
membersToAdd.removeAll(availableMembers);

membersToAdd now has all the members you need to add.

---

If you happen to have Java 8, there is an even simpler way to do this:

members.stream()
        .filter(p->!availableMembers.contains(p))
        .forEach(p->model2.addElement(p));

Answer 2

try this tricky way, add all to an ArrayList and remove those you do not want

ArrayList<Member> tmp = new ArrayList<Member>();
tmp.addAll(MembersArray);
tmp.removeAll(membersAvailableArray);
for(Member allMems: tmp){
    model2.addElement(allMems.getFirstName() + " " + allMems.getLastName());
}