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 valueimport 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 valueimport 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
