Compare two arrayList get common value and it should it not affect original values

public void commonId(ArrayList<ArrayList<String>> stylistIdList) {
if (stylistIdList.size() > 1) {
array1=stylistIdList.get(0);
array2=stylistIdList.get(1);
booleanStylistid=array1.retainAll(array2);
} else {
array1=stylistIdList.get(0);
}
}


Here I am having ArrayList<ArrayList<String>> stylistIdList contains two arraylist i want get common values from the two list.Its returning the common values but after getting common values the ArrayList<ArrayList<String>> stylistIdList value is changed into the values which is common.I want same values in ArrayList<ArrayList<String>> stylistIdList after getting common values.

ArrayList<ArrayList<String>> stylistIdList

arraylist

ArrayList<ArrayList<String>> stylistIdList

ArrayList<ArrayList<String>> stylistIdList

Example

ArrayList<ArrayList<String>> stylistIdLis = 0(0["abcdefgh"], ["abc"]), 1(0["abcdefgh"]);


output stylistIdList=("abcdefgh");

stylistIdList=("abcdefgh");

after getting output the ArrayList<ArrayList<String>> stylistIdLis values is changed into ArrayList<ArrayList<String>> stylistIdLis = 0("abcdefgh"), 1("abcdefgh");
But it i want like this

ArrayList<ArrayList<String>> stylistIdLis

ArrayList<ArrayList<String>> stylistIdLis = 0("abcdefgh"), 1("abcdefgh");

ArrayList<ArrayList<String>> stylistIdLis = 0(0["abcdefgh"],["abc"]), 1(0["abcdefgh"]);


1 Answer
1

retainAll modifies the list it is called on. If you want to get the common IDs without modifying the original lists, you need to return a new list.

retainAll

public ArrayList<String> commonIds(ArrayList<ArrayList<String>> lists) {
List<String> common = new ArrayList<>(lists.get(0));
if (lists.size() > 1) common.retainAll(lists.get(1));

return common;
}


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