How can i get the list of unselected elements?

Question

I have two arrayLists namely readAllNames and anotherone is selectedNames.now i want to get the anotherlist which having the unSelectedNames .ex.

List<Name>readAllNames = {"a","b","c","d","e","f","g"};
List<Name>selectedNames = {"a","b"};

how can i get the: unSelectedNames {"c","d","e","f","g"} from readAllNames?

without Using remove() And removeAll()

Try to use readAllNames.indexOf(object); object - element from selected names. — alnasfire, Feb 01 '13 at 12:49
If remove and removeAll are not working properly it may be because your Name class does not implement equals / hashcode properly. — ditkin, Feb 01 '13 at 12:51
here incase selectedNames having {"a","e"}means how can you use index ... — Arunprasad, Feb 01 '13 at 12:53

score 3 · Accepted Answer · edited Feb 01 '13 at 12:57

3

List<String> unread = new ArrayList<String>();
for(String s : readAllNames ){
    if(!selectedNames.contains(s))
        unread.add(s);
}

edited Feb 01 '13 at 12:57

Anders R. Bystrup

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answered Feb 01 '13 at 12:51

spiritwalker

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but Have to do override also http://stackoverflow.com/questions/2642589/how-does-a-java-arraylist-contains-method-evaluate-objects – Arunprasad Feb 01 '13 at 14:32

Anders R. Bystrup · Answer 2 · 2013-02-01T12:56:55.283

2

If you don't want to use remove()/removeAll() you could always iterate through readAllNames and for each element check if it is contains()'ed in selectedNames and if not add it to unselectedNames.

But you really should use removeAll(); show us your Name class and we can probably tell you what's wrong (hint: read up on equals() and hashCode() semantics wrt. Collection operations.)

Cheers,

edited Feb 01 '13 at 12:56

answered Feb 01 '13 at 12:50

Anders R. Bystrup

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score 0 · Answer 3 · answered Feb 01 '13 at 12:46

0

Why not take a look at the sourcecode for remove() and use that?

answered Feb 01 '13 at 12:46

bcz '@PostConstruct' method remove() and removeAll() not working properly.but those are working in junit test perfectly.i don't know the reason . – Arunprasad Feb 01 '13 at 12:49
1

Sorry I don't understand your response. remove() will definitely do what you want it to do. If it's not working then it's an issue with your data or parameters. – Feb 01 '13 at 12:50
1

This is probably because your Name class has not implemented equals / hashcode methods properly. – ditkin Feb 01 '13 at 12:52

score 0 · Answer 4 · answered Feb 01 '13 at 12:57

0

ArrayList<Name> unselectedName = new ArrayList<String>();
for(Name s: readAllNames){
    if(!selectedNames.contains(s)){
        unselectedName.add(s);
    }
}

answered Feb 01 '13 at 12:57

altsyset

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score 0 · Answer 5 · answered Feb 01 '13 at 13:02

0

Try this:

List<String> unSelectedNames = new ArrayList<String>(readAllNames);
unSelectedNames.removeAll(selectedNames);

You don't have to touch the original List, just the copy of that.

answered Feb 01 '13 at 13:02

gaborsch

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score 0 · Answer 6 · answered Feb 01 '13 at 13:11

0

try this

List<Name>readAllNames = {"a","b","c","d","e","f","g"};
List<Name>selectedNames = {"a","b"};
List<Name>unselectedNames = null;
Collections.copy(unselectedNames , readAllNames);
unselectedNames.removeAll(selectedNames);

answered Feb 01 '13 at 13:11

Srihari

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How can i get the list of unselected elements?

6 Answers6