ArrayList retainAll() method use for remove from this list all of its elements that are not contained in the given collection.
Syntax :
public boolean retainAll(Collection<?> c)
}
- Parameters:
c collection containing elements to be retained in this list - Returns Value :
true if this list changed as a result of the call - Exception Throws: It throws following exceptions
ClassCastException – if the class of an element of this list is incompatible with the specified collection (optional)
NullPointerException – if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null
Now will see ArrayList retainAll() method example in java
import java.util.ArrayList;
import java.util.List;
public class RetainAll {
public static void main(String[] args) {
ArrayList<String> arr = new ArrayList<String>();
// add element in arraylist
arr.add("c");
arr.add("php");
arr.add("html");
arr.add("java");
arr.add("delhi");
arr.add("INDIA");
// print arraylist
System.out.println("arrayList is = " + arr);
List<String> brr = new ArrayList<String>();
brr.add("java");
brr.add("shivam");
/*
* removes from arr all of its elements that are
* not contained in the brr.
*/
arr.retainAll(brr);
System.out.println("After retainAll arr is="+arr);
}
}
Output:
arrayList is = [c, php, html, java, delhi, INDIA]
After retainAll arr is=[java]