Last Updated : 02 Jan, 2019
This method is used to retain all the elements present in the collection from the specified collection into the list.
Syntax:boolean retainAll(Collection c)Parameters:
This method has only argument, collection of which elements are to be retained in the given list.
Returns:This method returns True if elements are retained and list changes. Below programs show the implementation of this method.
Program 1: Java
// Java code to show the implementation of
// retainAll method in list interface
import java.util.*;
public class GfG {
// Driver code
public static void main(String[] args)
{
// Initializing a list of type Linkedlist
List<Integer> l = new LinkedList<>();
l.add(1);
l.add(3);
l.add(5);
l.add(7);
l.add(9);
System.out.println(l);
ArrayList<Integer> arr = new ArrayList<>();
arr.add(3);
arr.add(5);
l.retainAll(arr);
System.out.println(l);
}
}
Output:
[1, 3, 5, 7, 9] [3, 5]Program 2:
Below is the code to show implementation of list.retainAll() using Linkedlist.
Java
// Java code to show the implementation of
// retainAll method in list interface
import java.util.*;
public class GfG {
// Driver code
public static void main(String[] args)
{
// Initializing a list of type Linkedlist
List<String> l = new LinkedList<>();
l.add("10");
l.add("30");
l.add("50");
l.add("70");
l.add("90");
System.out.println(l);
ArrayList<String> arr = new ArrayList<>();
arr.add("30");
arr.add("50");
l.retainAll(arr);
System.out.println(l);
}
}
Output:
[10, 30, 50, 70, 90] [30, 50]Reference: Oracle Docs
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