Java ArrayBlockingQueue add() Method

The add() method of ArrayBlockingQueue() appends the defined element at the tail end of the queue if the queue's capacity allows it.

The method returns true on successful insertion and throws an IllegalStateException if queue doesn't has enough capacity.

Syntax:

Parameters:

e - This is the element to be added.

Specified By:

The add() method of class ArrayBlockingQueue is specified by:

add() method in interface Queue<E>
add() method in interface Collection<E>
add() method in interface BlockingQueue<E>

Override:

The add() method of class ArrayBlockingQueue overrides the add() method of class AbstractQueue<E>.

Throws:

The add() method throws :

NullPointerException - If the element defined is null.

IllegalStateException - If the queue is full.

Return Value:

The add() method returns true(as defined by Collection.add(E)).

Example 1

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
    public class ArrayBlockingQueueAddExample1 {
        public static void main(String[] args) {
            int j =1;
            int capacity = 5;
                BlockingQueue<Integer> queue = new ArrayBlockingQueue<Integer>(capacity);
                for (int i = 1; i <= capacity; i++) {
                    //  Adding items add() to the tail of queue
                    queue.add(i);
                    System.out.println("After adding "+ j++ +" to the queue :");
                    System.out.println(queue);
                    System.out.println();
                }
            }
    }

Output:

After adding 1 to the queue :
[1]

After adding 2 to the queue :
[1, 2]

After adding 3 to the queue :
[1, 2, 3]

After adding 4 to the queue :
[1, 2, 3, 4]

After adding 5 to the queue :
[1, 2, 3, 4, 5]

Example 2

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
public class ArrayBlockingQueueAddExample2 {
    static int i =0;
     static int capacity =100;
    public static void main(String[] args) {
        // create a ArrayBlockingQueue
        BlockingQueue<String> queue = new ArrayBlockingQueue<String>(capacity);
        //  Adding items add() to the tail of queue
        queue.add("aman");
        queue.add("bhavika");
        for (String val : queue) {
            String upperCasec = val.toUpperCase();
            System.out.println(++i + " Lower case = " + val);
            System.out.println("  Upper case = " + upperCasec);
            System.out.println();
        }
    }
}

Output:

1 Lower case = aman
  Upper case = AMAN

2 Lower case = bhavika
  Upper case = BHAVIKA

Example 3

import java.util.Collections;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
public class ArrayBlockingQueueAddExample3 {
    public static void main(String[] args) {
        Integer[] val = {0, 1};
        int capacity = 100;
        BlockingQueue<Integer> queue = new ArrayBlockingQueue<Integer>(capacity);
        queue.add(71018);
        queue.add(8000);
        queue.add(1178);
        queue.add(1190);
        for (Integer n : queue) {
            System.out.println(n);
            val[0] = Collections.max(queue);
            val[1] = Collections.min(queue);
        }
        System.out.println("Max number = "+ val[0]);
        System.out.println("Min number = "+ val[1]);
    }
}

Output:

71018
8000
1178
1190
Max number = 71018
Min number = 1178

Example 4

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
public class ArrayBlockingQueueAddExample4 {
    public static void main(String[] args) {
    int capacity = 5;
    BlockingQueue<String> queue = new ArrayBlockingQueue<>(capacity);
    // add elements to the queue
        queue.add("Aman");
        queue.add("Bhavika");
        queue.add("Reema");
        queue.add("Salman");
        queue.add(null);
         for (String val:queue) {
             System.out.println("Name = " + queue);
         }
    }
}

Output:

Exception in thread "main" java.lang.NullPointerException
	at java.util.concurrent.ArrayBlockingQueue.checkNotNull(ArrayBlockingQueue.java:150)
	at java.util.concurrent.ArrayBlockingQueue.offer(ArrayBlockingQueue.java:325)
	at java.util.AbstractQueue.add(AbstractQueue.java:95)
	at java.util.concurrent.ArrayBlockingQueue.add(ArrayBlockingQueue.java:312)
	at com.javaTpoint.ArrayBlockingQueue_addMethodExample4.main(ArrayBlockingQueue_addMethodExample4.java:16)

If any specified element in the queue is null, it will give you NullPointerException as shown above.

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