The add(E) method of AbstractSet Class appends the specified element to the end of this AbstractSet.
Syntax:
boolean add(E element)
Parameters: This function accepts a single parameter element as shown in the above syntax. The element specified by this parameter is appended to end of the AbstractSet.
Return Value: This method returns True after successful execution, else False.
Exception: This method throws:
- UnsupportedOperationException: if the add operation is not supported by this collection
- ClassCastException: if the class of the specified element prevents it from being added to this collection
- NullPointerException: if the specified element is null and this collection does not permit null elements
- IllegalArgumentException: if some property of the element prevents it from being added to this collection
- IllegalStateException: if the element cannot be added at this time due to insertion restrictions
Below program illustrates the working of java.util.AbstractSet.add(E element) method:
Example 1:
// Java code to illustrate boolean add(E element)import java.util.*; public class AbstractSetDemo { public static void main(String args[]) { // Creating an empty AbstractSet AbstractSet<String> set = new TreeSet<String>(); // Use add() method // to add elements in the AbstractSet set.add("Geeks"); set.add("for"); set.add("Geeks"); set.add("10"); set.add("20"); // Output the present AbstractSet System.out.println("The AbstractSet is: " + set); // Adding new elements to the end set.add("Last"); set.add("Element"); // Printing the new AbstractSet System.out.println("The new AbstractSet is: " + set); }} |
Output:
The AbstractSet is: [10, 20, Geeks, for] The new AbstractSet is: [10, 20, Element, Geeks, Last, for]
Example 2: To demonstrate NullPointerException
// Java code to illustrate// boolean add(E element) import java.util.*; public class AbstractSetDemo { public static void main(String args[]) { // Creating an empty AbstractSet AbstractSet<Integer> set = new TreeSet<Integer>(); // Use add() method // to add elements in the AbstractSet set.add(10); set.add(20); set.add(30); set.add(40); set.add(50); // Output the present AbstractSet System.out.println("The AbstractSet is: " + set); System.out.println("Trying to add null"); try { // Adding null set.add(null); } catch (Exception e) { System.out.println(e); } }} |
Output:
The AbstractSet is: [10, 20, 30, 40, 50] Trying to add null java.lang.NullPointerException
