Collection Interface retainAll() Method

Removes all elements from the invoking collection except those in collection.

Collection Interface retainAll() Method:

Removes all elements from the invoking collection except those in collection. It returns true if the collection changed. Otherwise, returns false.

Syntax :

boolean retainAll(Collection collection);

Example :

import java.util.*;

public class CollectionInterfaceRetainAllMethod {
public static void main(String[] args){
Collection collection = new LinkedList();
ArrayList arraylist = new ArrayList();
collection.add(1);
collection.add(2);
collection.add(3);
collection.add(4);

arraylist.add(1);
arraylist.add(2);
System.out.println("Before retainAll :" + collection);
collection.retainAll(arraylist);
System.out.println("After retainAll :" + arraylist);
System.out.println("After retainAll :" + collection);
}
}

Output :

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