Create multiple Lists from one (Group List's Objects by a specific field)

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Given that I have the array of :

List<CustEnt> bulkList= CustRepo.fetchData();
//System.out.println(bulkList) -->

gives me :

    CustEct(name:"kasis",age:24,surname:"kumar"),CustEct(name:"samika",age:50,surname:"sharma"),CustEct(name:"manoj",age:84surname:"kumar")
OR
bulkList.get(1) --> CustEct(name:"kasis",age:24,surname:"kumar")

I want to create a new array which is grouped by the 3rd parameter of surname object. So that my array becomes

ArrayFinal = [CustEct(name:"kasis",age:24,surname:"kumar"),CustEct(name:"samika",age:50,surname:"sharma")],CustEct(name:"manoj",age:84surname:"kumar")

So that when we do .get(1) we would get object of kasis and samika.

Need the help in respective to java 8. I heard that we can use the Map ,but can anyone give the small code sample or any other implementation guide.

java-stream dictionary arrays java
2 Answers

A Map tracks key-value pairs.

  • Your key is the surname string.
  • Your value is a list of the CustEnt objects carrying that surname.
Map<String, List<CustEnt>>

Modern syntax with streams and lambdas makes for brief code to place your objects in a map.

Something like:

Map<String, List<CustEnt>> map = originalList.stream.collect(Collectors.groupingBy(CustEnt::getSurename));
user_14779940 
Map<String, List<CustEntity>> NamesList
        = bulkList.stream()
        .collect(Collectors.groupingBy(CustEntity::getSurames));

for (Map.Entry<String, List<CustEntity>> entry: NamesList.entrySet()) {
    ExcelGenerationService exp = new ExcelGenerationService( entry.getValue());
//service call
    exp.export(entry.getKey());
}
user_147111750
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