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); } } |
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); } } } |
The AbstractSet is: [10, 20, 30, 40, 50] Trying to add null java.lang.NullPointerException
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