I want to write below scenario using Java8. I am not sure how to explain it further, please comment if you have any doubts.

class A{     List<B> values;  }  class B{  }  //Assume some values List<String> list = ["val1","val2"]; //Assume some values Map<String, A> map = { "val1" : [A object] , "val2" : [A object] }; B b = new B();  //Iterate over every value in list for(String each: list){     //if map has a key with the value inside the list     A a = map.get(each);      //A has a list called "values" of B class objects. If that list is not null or empty add a new B object (b )in our case to the a List else initialze a new List and add the value there.     if(a.values != null && !a.values.isEmpty()){         a.values.add(b);     }else{         List<B> bList = new ArrayList<>();         bList.add(b);         a.values = bList;     } }