AbstractSequentialList retainAll() method in Java with Example Last Updated : 12 Dec, 2022 Comments Improve Suggest changes Like Article Like Report The retainAll() method of java.util.AbstractSequentialList class is used to retain from this list all of its elements that are contained in the specified collection. Syntax: public boolean retainAll(Collection c) Parameters: This method takes collection c as a parameter containing elements to be retained from this list. Returns Value: This method returns true if this list changed as a result of the call. Exception: This method throws 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. Below are the examples to illustrate the retainAll() method. Example 1: Java // Java program to demonstrate // retainAll() method for Integer value import java.util.*; public class GFG1 { public static void main(String[] argv) throws Exception { try { // Creating object of AbstractSequentialList<Integer> AbstractSequentialList<Integer> arrlist1 = new LinkedList<Integer>(); // Populating arrlist1 arrlist1.add(1); arrlist1.add(2); arrlist1.add(3); arrlist1.add(4); arrlist1.add(5); // print arrlist1 System.out.println("AbstractSequentialList before " + "retainAll() operation : " + arrlist1); // Creating another object of AbstractSequentialList<Integer> AbstractSequentialList<Integer> arrlist2 = new LinkedList<Integer>(); arrlist2.add(1); arrlist2.add(2); arrlist2.add(3); // print arrlist2 System.out.println("Collection Elements" + " to be retained : " + arrlist2); // Removing elements from arrlist // specified in arrlist2 // using retainAll() method arrlist1.retainAll(arrlist2); // print arrlist1 System.out.println("AbstractSequentialList after " + "retainAll() operation : " + arrlist1); } catch (NullPointerException e) { System.out.println("Exception thrown : " + e); } } } Output:AbstractSequentialList before retainAll() operation : [1, 2, 3, 4, 5] Collection Elements to be retained : [1, 2, 3] AbstractSequentialList after retainAll() operation : [1, 2, 3] Example 2: For NullPointerException Java // Java program to demonstrate // retainAll() method for Integer value import java.util.*; public class GFG1 { public static void main(String[] argv) throws Exception { try { // Creating object of AbstractSequentialList<Integer> AbstractSequentialList<Integer> arrlist1 = new LinkedList<Integer>(); // Populating arrlist1 arrlist1.add(1); arrlist1.add(2); arrlist1.add(3); arrlist1.add(4); arrlist1.add(5); // print arrlist1 System.out.println("AbstractSequentialList before " + "retainAll() operation : " + arrlist1); // Creating another object of AbstractSequentialList<Integer> AbstractSequentialList<Integer> arrlist2 = null; // print arrlist2 System.out.println("Collection Elements" + " to be retained : " + arrlist2); System.out.println("\nTrying to pass " + "null as a specified element\n"); // Removing elements from arrlist // specified in arrlist2 // using retainAll() method arrlist1.retainAll(arrlist2); // print arrlist1 System.out.println("AbstractSequentialList after " + "retainAll() operation : " + arrlist1); } catch (NullPointerException e) { System.out.println("Exception thrown : " + e); } } } Output:AbstractSequentialList before retainAll() operation : [1, 2, 3, 4, 5] Collection Elements to be retained : null Trying to pass null as a specified element Exception thrown : java.lang.NullPointerException Comment More infoAdvertise with us Next Article AbstractSequentialList subList() method in Java with Example C code_r Follow Improve Article Tags : Java Java-Collections Java - util package Java-Functions java-AbstractSequentialList +1 More Practice Tags : JavaJava-Collections Similar Reads AbstractSequentialList in Java with Examples The AbstractSequentialList class in Java is a part of the Java Collection Framework and implements the Collection interface and the AbstractCollection class. 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