How to handle null while comparing maps using streams - Java?

Question

I have 2 data structures with values like:

List<Map<String,String>> customerDirectory

[{NAME=ALEX BENSON, PHONE=012-12342, ADDRESS=123 MAIN ST, CITY=QUEENS, STATE=NY},
 {NAME=ZOYE ABEL, PHONE=012-12445, ADDRESS=123 WATERSIDE, CITY=WINDSOR, STATE=CT}]

and

Map<String,String> customerInfo

{NAME=ALEX BENSON, PHONE=012-12342, ADDRESS=123 MAIN ST}

I am trying to iterate through the customerDirectory to find if customerInfo has exact match in values for the keys - "NAME","PHONE","ADDRESS" so that I could find if the record is a duplicate.

So I have come up with:

List<String> compareKeys = Arrays.asList("NAME","PHONE","ADDRESS");

Function<Map<String,String>, String> getVal = mp -> compareKeys.stream().map(mp::get).map(String::trim).collect(Collectors.joining());

BiPredicate<Map<String,String>, Map<String,String>> checkDup = (mp1,mp2) -> getVal.apply(mp1).equals(getVal.apply(mp2));

boolean anyMatch = customerDirectory.stream().anyMatch(customer-> checkDup.test(customerInfo, customer));

But the customerInfo map can have value for ADDRESS as null for which I have tried:

BiFunction<Map<String, String>, String, String> handleNull = (mp, key) -> mp.get(key) == null ? " " : mp.get(key);

and I have used it in :

Function<Map<String,String>, String> getVal = mp -> compareKeys.stream().map(key->handleNull.apply(mp,key)).map(mp::get).map(String::trim).collect(Collectors.joining());

But I still end up getting NullPointerException which means I am missing the exact flow probably. Is there a better way to handle null values here?

Ehab Qadah · Accepted Answer · 2020-05-30 18:30:15Z

5

If i correctly understood your question then you just want to find out is there any exact match or not, and you want to keep your answer in anyMatch. Please try to update your code with below one.

Function<Map<String, String>, String> getVal = mp -> 
    compareKeys.stream().map(mp::get).filter(Objects::nonNull).map(String::trim)
            .collect(Collectors.joining());

edited May 30, 2020 at 18:30

Ehab Qadah

5704 silver badges12 bronze badges

answered May 30, 2020 at 16:19

Mr. Jain

1461 gold badge3 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Hadi · Accepted Answer · 2020-05-30 17:51:46Z

4

You can do it in a better way I think.

boolean anyMatch = customerDirectory.stream()
         .anyMatch(m -> m.entrySet().stream()
           .filter(entry -> compareKeys.contains(entry.getKey()))
           .allMatch(entry -> entry.getValue().equals(customerInfo.get(entry.getKey()))));

or even more concise:

 boolean anyMatch =
            customerDirectory.stream()
                   .anyMatch(m -> compareKeys.stream()
                            .allMatch(key -> m.get(key).equals(customerInfo.get(key))));

edited May 30, 2020 at 17:51

answered May 30, 2020 at 17:27

Hadi

17.3k4 gold badges41 silver badges63 bronze badges

5 Comments

k92 Over a year ago

won't this give NullPointer for customerInfo ADDRESS value when it is null like I have mentioned in the question?

Eklavya Over a year ago

2nd solution is better, without filtering

k92 Over a year ago

Yeah this is surely better but not working for map when {ADDRESS=null}, Tried to add filter after compareKeys.stream() but still getting NullPointer.

Hadi Over a year ago

which Map do you mean? see demo

k92 Over a year ago

Correct, the filter I was adding was causing problem. Thanks a lot!

Collectives™ on Stack Overflow

How to handle null while comparing maps using streams - Java?

2 Answers 2

Comments

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related