Compare two lists of different objects by certain two fields

Question

I have two lists of different objects

class objectA {
String aId;
String aTitle;
String aUrl;
...
}
class objectB {
String bId;
String bTitle;
String bUrl;
...
}

List<ObjectA> aObjectList;
List<ObjectB> bObjectList;

I need to verify that these two lists have equal values for Id and Title fields. The way I see is to create Map<String, String> from two lists and then compare them.

List<Map<String, String>> aObjectMapList = aObjectList.stream()...
List<Map<String, String>> bObjectMapList = bObjectList.stream()...

But maybe assertj has an appropriate approach to solve my issue?

I would be grateful for any solution to my issue via stream or assertj or somehow else.

@MCEmperor yes, they will have the equal size from the beginning. — Ip Man, Sep 02 '21 at 10:34

score 2 · Answer 1 · answered Sep 02 '21 at 10:21

I'd make a string id+title for each object, in 2 lists. Then compare the 2 lists

List<String> aList = aObjectList.stream()
   .map(a -> a.getaId() + a.getaTitle())
   .collect(Collectors.toList());
List<String> bList = bObjectList.stream()
   .map(b -> b.getbId() + b.getbTitle())
   .collect(Collectors.toList());

boolean sameElements = aList.size() == bList.size() && 
                       aList.containsAll(bList) && 
                       bList.containsAll(aList);

score 1 · Accepted Answer · answered Sep 02 '21 at 10:21

It could make sense to merge id / title into a single String, remap the input lists into List<String> and then use AssertJ hasSameElements to compare the new lists:

assertThat(
    aObjectList.stream()
               .map(a -> String.join(":", a.aId, a.aTitle))
               .collect(Collectors.toList())
).hasSameElementsAs(
    bObjectList.stream()
               .map(b -> String.join(":", b.bId, b.bTitle))
               .collect(Collectors.toList())

);

Compare two lists of different objects by certain two fields

2 Answers2