Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17


Junit assertCollection?

Posted on 2011-03-14
Medium Priority
Last Modified: 2012-05-11
What's the best way to unit test that 2 collections are the same.
(Not the same object, but each element value of one collection is in the other, and vice versa)
Question by:allelopath
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
LVL 47

Expert Comment

ID: 35132060

Are all objects in your collections unique?
Or you may have two equal options present in any of your two collections?

if they are unique then if the sizes of both collections are equal,
and then you just traverse one collection and check that
all elements of this coll;ection are present in the second collection then
tyour collections are the same in the sense you mentioned
LVL 47

Expert Comment

ID: 35132107

if my question above has the anser "yes" then this method should work:

boolean areTheyEqual(ArrayList a1, ArrayList a2){
if(a1.size() != a2.size() ) return false;

for(int j=0; j<a1.size(); j++){
return false;
return true;


LVL 47

Accepted Solution

for_yan earned 2000 total points
ID: 35132225

I think this should work even if each collection
has identical items:

boolean areTheyEqual(ArrayList a1, ArrayList a2){
if(a1.size() != a2.size() ) return false;
for(int j =0; j<a1.size(); j++){
int count1 = 0;
for(int k=0; k<a1.size(); k++){

int count2 = 0;
for(int k=0; k<a2.size(); k++){

if(count1 != count2)return false;

retrurn true;

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!


Author Comment

ID: 35132239
Looks like I could also use Apache Commons CollectionsUtils
CollectionUtils.isEqualCollection(actual, expected);
LVL 47

Expert Comment

ID: 35132266
Yes, you are right - that probably would be better.
But it is nice to invent the wheel also :)
LVL 86

Expert Comment

ID: 35132479
boolean identical = coll1.size() == 0;

Featured Post

Enroll in September's Course of the Month

This month’s featured course covers 16 hours of training in installation, management, and deployment of VMware vSphere virtualization environments. It's free for Premium Members, Team Accounts, and Qualified Experts!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Java had always been an easily readable and understandable language.  Some relatively recent changes in the language seem to be changing this pretty fast, and anyone that had not seen any Java code for the last 5 years will possibly have issues unde…
Introduction Java can be integrated with native programs using an interface called JNI(Java Native Interface). Native programs are programs which can directly run on the processor. JNI is simply a naming and calling convention so that the JVM (Java…
The viewer will learn how to implement Singleton Design Pattern in Java.
This tutorial will introduce the viewer to VisualVM for the Java platform application. This video explains an example program and covers the Overview, Monitor, and Heap Dump tabs.
Suggested Courses

715 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question