The Java.util.concurrent.CopyOnArrayList.retainAll() method in Java is used to retain only the elements in the list that are contained in specific collection.
Syntax:
public boolean retainAll(Collection col)
Parameters: This method accepts a mandatory parameter col which is of the type of collection. This is the collection of elements to be retained in this vector.
Return Type: This method returns a boolean value true if the list is changed at all as a result of call else false.
Exception: This method throws a NullPointerException if the specified collection is NULL.
Below Programs illustrate the retainAll() method of CopyOnArrayList in Java:
Program 1: This program involves CopyOnArraylist retainAll() method of Integer Type:
// Java Program to illustrate CopyOnArrayList// retainAll() methodimport java.util.concurrent.CopyOnWriteArrayList;import java.util.*; public class GFG { public static void main(String[] args) { // create object of CopyOnWriteArrayList CopyOnWriteArrayList<Integer> ArrLis1 = new CopyOnWriteArrayList<Integer>(); // Add elements ArrLis1.add(34); ArrLis1.add(66); ArrLis1.add(72); ArrLis1.add(10); // print CopyOnWriteArrayList System.out.println("CopyOnWriteArrayList1: " + ArrLis1); // create object of CopyOnWriteArrayList CopyOnWriteArrayList<Integer> ArrLis2 = new CopyOnWriteArrayList<Integer>(); // Add elements ArrLis2.add(10); ArrLis2.add(66); ArrLis2.add(97); // print CopyOnWriteArrayList System.out.println("CopyOnWriteArrayList2: " + ArrLis2); // Applying the function ArrLis2.retainAll(ArrLis1); // print CopyOnWriteArrayLists System.out.println("After applying retainAll()" + " method on ArrLis2"); System.out.println("CopyOnWriteArrayList1: " + ArrLis1); System.out.println("CopyOnWriteArrayList2: " + ArrLis2); }} |
CopyOnWriteArrayList1: [34, 66, 72, 10] CopyOnWriteArrayList2: [10, 66, 97] After applying retainAll() method on ArrLis2 CopyOnWriteArrayList1: [34, 66, 72, 10] CopyOnWriteArrayList2: [10, 66]
Program 2: This program involves CopyOnArraylist retainAll() method of String Type:
// Java Program to illustrate CopyOnArrayList// retainAll() method import java.util.concurrent.CopyOnWriteArrayList;import java.util.*; public class GFG { public static void main(String[] args) { CopyOnWriteArrayList<String> ArrLis1 = new CopyOnWriteArrayList<String>(); // Add elements ArrLis1.add("geeks"); ArrLis1.add("shaan"); ArrLis1.add("gfg"); ArrLis1.add("programming"); // print CopyOnWriteArrayList System.out.println("CopyOnWriteArrayList1: " + ArrLis1); // create object of CopyOnWriteArrayList CopyOnWriteArrayList<String> ArrLis2 = new CopyOnWriteArrayList<String>(); // Add elements ArrLis2.add("geeks"); ArrLis2.add("gfg"); ArrLis2.add("qwe"); // print CopyOnWriteArrayList System.out.println("CopyOnWriteArrayList2: " + ArrLis2); // Applying the function ArrLis2.retainAll(ArrLis1); // print CopyOnWriteArrayLists System.out.println("After applying retainAll()" + " method on ArrLis2"); System.out.println("CopyOnWriteArrayList1: " + ArrLis1); System.out.println("CopyOnWriteArrayList2: " + ArrLis2); }} |
CopyOnWriteArrayList1: [geeks, shaan, gfg, programming] CopyOnWriteArrayList2: [geeks, gfg, qwe] After applying retainAll() method on ArrLis2 CopyOnWriteArrayList1: [geeks, shaan, gfg, programming] CopyOnWriteArrayList2: [geeks, gfg]