Java ArrayBlockingQueue size() Method

Last Updated : 17 Mar 2025

The size() method of Java ArrayBlockingQueue class returns the total number of elements in the ArrayBlockingQueue.

Syntax:

Parameters:

Specified By:

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

Size in interface Collection<E>.
Size in class AbstractCollection<E>

Return Value:

The size() method returns the total number of elements in this queue.

Example 1

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

public class ArrayBlockingQueueSizeExample1 {
    public static void main(String[] args) {
        int capacity = 10;
        BlockingQueue<Integer> queue = new ArrayBlockingQueue<Integer>(capacity);
        queue.add(67);
        queue.add(109);
        queue.add(98);
        queue.add(123);
        queue.add(100);
        int val = queue.size();
        System.out.println("Total elements in the queue = "+val);
        System.out.println("Elements are :");
        for(Integer xyz : queue){
            System.out.println(xyz);
        }
    }
}

Output:

Total elements in the queue = 5
Elements are :
67
109
98
123
100

Example 2

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ArrayBlockingQueue;

class Patients{
    String Pname;
    public Patients(String pname) {
        Pname = pname;
    }
    public String toString(){
        return this.Pname;
    }
}
public class ArrayBlockingQueueSizeExample2 {
    public static void main(String[] args) {
        Patients patient1 = new Patients("Megha");
        Patients patient2 = new Patients("Reema");
        Patients patient3 = new Patients("Supriya");
        Patients patient4 = new Patients("Anoop");
        Patients patient5 = new Patients("Sonia");
        Patients patient6 = new Patients("Tejashvi");
        List<Patients> list = new ArrayList<Patients>();
        int capacity = 100;
        ArrayBlockingQueue<Patients> queue = new ArrayBlockingQueue<Patients>(capacity);
        queue.add(patient1);
        queue.add(patient2);
        queue.add(patient3);
        queue.add(patient4);
        queue.add(patient5);
        queue.add(patient6);
        list.add(patient1);
        list.add(patient2);
        list.add(patient3);
        list.add(patient4);
        // returns the total size of the queue
        System.out.println("Total Patients = "+queue.size());
        for(Patients xyz : queue){
            System.out.println(xyz);
        }
        System.out.println();
        System.out.println("Patients recovered and discharged : "+list);
        System.out.println();
        queue.removeAll(list);
        System.out.println("Patients left in the hospital = "+queue.size());
        for (Patients xyz : queue) {
            System.out.println(xyz);
        }
    }
}

Output:

Total Patients = 6
Megha
Reema
Supriya
Anoop
Sonia
Tejashvi

Patients recovered and discharged : [Megha, Reema, Supriya, Anoop]

Patients left in the hospital = 2
Sonia
Tejashvi

Example 3

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

public class ArrayBlockingQueueSizeExample3 {
    public static void main(String[] args) {
        int capacity = 10;
        BlockingQueue<String> queue = new ArrayBlockingQueue<String>(capacity);
        queue.add(null);
        queue.add(null);
        int val =queue.size();
        System.out.println("Size of queue = "+val);
    }
}

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.ArrayBlockingQueueSizeExample3.main(ArrayBlockingQueueSizeExample3.java:10)

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Java ArrayBlockingQueue size() Method

Syntax:

Parameters:

Specified By:

Return Value:

Example 1

Example 2

Example 3

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