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How to retain elements from a Collection in another Collection
Let’s say the following is our Collection i.e. ArrayList −
List<Integer>list = new ArrayList<Integer>(); list.add(100); list.add(200); list.add(200); list.add(200); list.add(300); list.add(400); list.add(400); list.add(500);
Now, create another Collection −
List <Integer> list2 = new ArrayList<Integer>(); list2.add(100); list2.add(200); list2.add(300); list2.add(400);
To retain all elements from a Collection in another Collection, try the following with list and list2 as our two Collections −
list.retainAll(list2);
Example
import java.util.ArrayList; import java.util.List; public class Demo { public static void main(String args[]) throws Exception { List<Integer>list = new ArrayList<Integer>(); list.add(100); list.add(200); list.add(200); list.add(200); list.add(300); list.add(400); list.add(400); list.add(500); List <Integer>list2 = new ArrayList<Integer>(); list2.add(100); list2.add(200); list2.add(300); list2.add(400); list.retainAll(list2); System.out.println("Resultant list = "+list); } }
Output
Resultant list = [100, 200, 200, 200, 300, 400, 400]
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