Queue add() method in Java

26 Sep, 2018
The add(E e) method of Queue Interface inserts the element passed in the parameter to the end of the queue if there is space. If the Queue is capacity restricted and no space is left for insertion, it returns an IllegalStateException. The function returns true on successful insertion.
Syntax:
boolean add(E e)
Parameters: This method accepts a mandatory parameter e which is the element to be inserted in the end of the Queue.
Returns: This method returns true on successful insertion.
Exceptions: The function throws four exceptions which are described as below:
ClassCastException: when the class of the element to be entered prevents it from being added to this container.
IllegalStateException: when the capacity of the container is full and insertion is done.
IllegalArgumentException: when some property of the element prevents it to be added to the queue.
NullPointerException: when the element to be inserted is passed as null and the Queue’s interface does not allow null elements.
Below programs illustrate add() method of Queue:
Program 1: With the help of LinkedList.
// Java Program Demonstrate add()// method of Queue  import java.util.*;  public class GFG {    public static void main(String[] args)        throws IllegalStateException    {          // create object of Queue        Queue<Integer> Q            = new LinkedList<Integer>();          // Add numbers to end of Queue        Q.add(7855642);        Q.add(35658786);        Q.add(5278367);        Q.add(74381793);          // before removing print queue        System.out.println("Queue: " + Q);    }}
Queue: [7855642, 35658786, 5278367, 74381793]

Program 2: With the help of ArrayDeque.
// Java Program Demonstrate add()// method of Queue  import java.util.*;  public class GFG {    public static void main(String[] args)        throws IllegalStateException    {          // create object of Queue        Queue<Integer> Q            = new ArrayDeque<Integer>();          // Add numbers to end of Queue        Q.add(7855642);        Q.add(35658786);        Q.add(5278367);        Q.add(74381793);          // before removing print queue        System.out.println("Queue: " + Q);    }}
Queue: [7855642, 35658786, 5278367, 74381793]

Program 3: With the help of LinkedBlockingDeque.
// Java Program Demonstrate add()// method of Queue  import java.util.*;import java.util.concurrent.LinkedBlockingDeque;  public class GFG {    public static void main(String[] args)        throws IllegalStateException    {          // create object of Queue        Queue<Integer> Q            = new LinkedBlockingDeque<Integer>();          // Add numbers to end of Queue        Q.add(7855642);        Q.add(35658786);        Q.add(5278367);        Q.add(74381793);          // before removing print queue        System.out.println("Queue: " + Q);    }}
Queue: [7855642, 35658786, 5278367, 74381793]

Program 4: With the help of ConcurrentLinkedDeque.
// Java Program Demonstrate add()// method of Queue  import java.util.*;import java.util.concurrent.ConcurrentLinkedDeque;  public class GFG {    public static void main(String[] args)        throws IllegalStateException    {          // create object of Queue        Queue<Integer> Q            = new ConcurrentLinkedDeque<Integer>();          // Add numbers to end of Queue        Q.add(7855642);        Q.add(35658786);        Q.add(5278367);        Q.add(74381793);          // before removing print queue        System.out.println("Queue: " + Q);    }}
Queue: [7855642, 35658786, 5278367, 74381793]

Below programs illustrate exceptions thrown by this method:
Program 5: To show NullPointerException.
// Java Program Demonstrate add()// method of Queue when Null is passed  import java.util.*;import java.util.concurrent.LinkedBlockingQueue;  public class GFG {    public static void main(String[] args)        throws IllegalStateException    {          // create object of Queue        Queue<Integer> Q            = new LinkedBlockingQueue<Integer>();          // Add numbers to end of Queue        Q.add(7855642);        Q.add(35658786);        Q.add(5278367);          try {            // when null is inserted            Q.add(null);        }        catch (Exception e) {            System.out.println("Exception: " + e);        }    }}
Exception: java.lang.NullPointerException

Program 6: To show IllegalStateException.
// Java Program Demonstrate add()// method of Queue when capacity is fullimport java.util.*;import java.util.concurrent.LinkedBlockingQueue;  public class GFG {    public static void main(String[] args)        throws IllegalStateException    {          // create object of Queue        Queue<Integer> Q            = new LinkedBlockingQueue<Integer>(3);          // Add numbers to end of Queue        Q.add(7855642);        Q.add(35658786);        Q.add(5278367);          try {            // when capacity is full            Q.add(10);        }        catch (Exception e) {            System.out.println("Exception: " + e);        }    }}
Exception: java.lang.IllegalStateException: Queue full

Note: The other two exceptions are internal and are caused depending on the compiler hence cannot be shown in the compiler.
Reference: https://docs.oracle.com/javase/8/docs/api/java/util/Queue.html#add-E-
Java - util package
java-basics
Java-Collections
Java-Functions
java-queue
Java
Java
Java-Collections
Writing code in comment?
Please use ide.geeksforgeeks.org,
generate link and share the link here.