The removeAll() method in CopyOnWriteArrayList class that removes all the elements that are contained in the specified collection from the CopyOnArrayList object you call on.
Syntax:
public boolean removeAll(Collection collection)
Parameter: The method accepts only a single parameter collection which is to be removed from the calling object.
Return Value: This method returns a boolean value. It returns true if this remove operation is successful.
Exception: This method throws following exceptions:
- ClassCastException: if the class of an element of this list is incompatible with the specified collection.
- NullPointerException: if the specified collection is null or if this list contains a null element and the specified collection does not permit null elements.
Below examples illustrates the removeAll() method:
Example 1:
// Java program to demonstrate removeAll() method import java.util.ArrayList;import java.util.concurrent.CopyOnWriteArrayList; public class Demo { public static void main(String args[]) { // Get the CopyOnWriteArrayList CopyOnWriteArrayList<String> wishlist = new CopyOnWriteArrayList<>(); // Add the elements in the CopyOnWriteArrayList wishlist.add("TV"); wishlist.add("computer"); wishlist.add("play station"); wishlist.add("mobile"); wishlist.add("smart watch"); // Print the CopyOnWriteArrayList System.out.println("CopyOnWriteArrayList: \n" + wishlist); // Get the collection to be removed ArrayList<String> checkList = new ArrayList<>(); checkList.add("play station"); checkList.add("TV"); checkList.add("mobile"); System.out.println("\nCollection to be removed:\n" + checkList); // Remove the collection from CopyOnWriteArrayList // using removeAll() method wishlist.removeAll(checkList); // Print the CopyOnWriteArrayList after removal System.out.println("\nAfter removal of collection" + " from CopyOnWriteArrayList:\n" + wishlist); }} |
Output:
CopyOnWriteArrayList: [TV, computer, play station, mobile, smart watch] Collection to be removed: [play station, TV, mobile] After removal of collection from CopyOnWriteArrayList: [computer, smart watch]
Example 2: To show NullPointerException
// Java program to demonstrate removeAll() method import java.util.ArrayList;import java.util.concurrent.CopyOnWriteArrayList; public class Demo { public static void main(String args[]) { // Get the CopyOnWriteArrayList CopyOnWriteArrayList<String> wishlist = new CopyOnWriteArrayList<>(); // Add the elements in the CopyOnWriteArrayList wishlist.add("TV"); wishlist.add("computer"); wishlist.add("play station"); wishlist.add("mobile"); wishlist.add("smart watch"); // Print the CopyOnWriteArrayList System.out.println("CopyOnWriteArrayList: \n" + wishlist); // Get the collection to be removed ArrayList<String> checkList = null; System.out.println("\nCollection to be removed: " + checkList); try { // Remove the collection from CopyOnWriteArrayList // using removeAll() method wishlist.removeAll(checkList); } catch (Exception e) { // Print the Exception System.out.println("\nException thrown" + " while removing null " + "from the CopyOnWriteArrayList: \n" + e); } }} |
Output:
CopyOnWriteArrayList: [TV, computer, play station, mobile, smart watch] Collection to be removed: null Exception thrown while removing null from the CopyOnWriteArrayList: java.lang.NullPointerException
