How to get duplicated and non duplicated element of arrayList?

Using standard JVM structures (MultiMap is provided by guava), you can do that.

Using standard JVM structures (MultiMap is provided by guava), you can do that: public List getDuplicates(final List l) { final HashMap m = new HashMap(); final List ret = new ArrayList(); String cnk; for (final Riviz r: l) { cnk = r.getCnk(); if (!m. Contains(cnk)) m. Add(cnk, new ArrayList()); m.

Get(cnk). Add(r); } List tmp; for (final Map. Entry entry: m.entrySet()) { tmp = entry.getValue(); if (tmp.size() == 1) // no dups continue; ret.

AddAll(tmp); } return ret; } ret will contain the duplicates. You can change that function to return a Map instead, and filter out entries where the list size is only one. You'll then get a map with the conflicting cnks as keys and a list of dups as values.

I can't change any thing in Riviz class.it is out of my control. Is there any other way to get duplicated and non duplicated in the arrayList? – itro Dec 22 '11 at 13:53 Then use a Comparator.

– fge Dec 22 '11 at 14:00 See edited answer: this probably answers your problem. – fge Dec 22 '11 at 14:13 I never used Comparator befor. Can you give me a hint or example?

– itro Dec 22 '11 at 14:29 In fact you don't need it, as demonstrated by my anwser. But if you want to write one, write a class which implements Comparator. You'll need to implement the compare() method, for instance: int compare(final Riviz r1, final Riviz r2) { return r1.getCnk().

CompareTo(r2.getCnk()); } – fge Dec 22 '11 at 14:32.

I am not clear exactly what you want however I suspect you want something like this. MultiMap multiMap = List list = for(Riziv r: list) multiMap. Put(r.getCnk(), r); for(Key cnk: multiMap.keySet()) { Collection sameCnk = multiMap.

Get(cnk); // check size and compare entries } The multi-map will have the list of Riziv objects for each Cnk.

Yes indeed. This is what I need for similar and non similar elemet inside arrayList. How can I compare the element's cnk?

– itro Dec 22 '11 at 14:07 Pity that MultiMap isn't standard in the JDK ;) – fge Dec 22 '11 at 14:08 @itro I have added an example for getting all the elements with the same cnk. – Peter Lawrey Dec 22 '11 at 14:21.

One way to do it is write a comparator to sort the list by cnk String and then compare each consecutive cnk String to the next, if you find a duplicate, they will be right next to eachother. 1. ) Sort the list using a comparator by sorting on the cnk variable.2.

) Compare each element in the list to the next for duplicates. There's probably many other ways to solve this, this is just the first that came to mind. I did not test this so you have been forewarned lol: ArrayList rizArray = new ArrayList(); //Sort the array by the CNK variable.

Collections. Sort(rizArray, new Comparator(){ @Override public int compare(Riziv arg0, Riziv arg1) { //Return the comparison of the Strings. //Use .

CompareToIgnoreCase if you want to ignore upper/lower case. Return arg0.getCnk(). CompareTo(arg1.getCnk()); } }); //List should be in alphabetical order at this point.

List duplicates = new ArrayList(); Riziv rizPrevious = null; for(Riziv riz: rizArray){ if(rizPrevious == null){ rizPrevious = riz; continue; } if(riz.getCnk(). CompareTo(rizPrevious.getCnk()) == 0){ duplicates. Add(riz); } rizPrevious = riz; }.

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