How can I turn a List of Lists into a List in Java 8?

Answer 1

I just want to explain one more scenario like List, this list contains a few more lists of other documents like List, List, List. So the structure is

class A {
  List documentList;
}

class Documents {
  List excels;
  List words;
  List ppt;
}

Now if you want to iterate Excel only from documents then do something like below..

So the code would be

 List documentList = new A().getDocumentList();

 //check documentList as not null

 Optional excelOptional = documentList.stream()
                         .map(doc -> doc.getExcel())
                         .flatMap(List::stream).findFirst();
 if(excelOptional.isPresent()){
   Excel exl = optionalExcel.get();
   // now get the value what you want.
 }

I hope this can solve someone's issue while coding...