BlockingQueue remainingCapacity() method in Java with examples

Last Updated : 12 Jul, 2025
The remainingCapacity() method of BlockingQueue returns the number of more elements that can be added to BlockingQueue without blocking. The Capacity returned arises in three cases:
  • If remaining Capacity is Zero, then no more elements can be added to the BlockingQueue.
  • If remaining Capacity of BlockingQueue is equal to the size of the Queue, then no element can be removed from the queue because in such situation queue is empty.
  • In any other case, Capacity is always equal to a difference between the initial capacity of this BlockingQueue and the current size of this BlockingQueue.
Syntax: 
public int remainingCapacity()
Return Value: This method returns the remaining capacity of the BlockingQueue. Note: The remainingCapacity() method of BlockingQueue has been inherited from the Queue class in Java. Below programs illustrates remainingCapacity() method of BlockingQueue class: Program 1: Java 
// Java Program Demonstrate remainingCapacity()
// method of BlockingQueue

import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.BlockingQueue;
public class GFG {

    public static void main(String[] args)
    {
        // define capacity of BlockingQueue
        int capacityOfQueue = 7;

        // create object of BlockingQueue
        BlockingQueue<String> BQ
            = new LinkedBlockingQueue<String>(
                capacityOfQueue);

        // Add element to BlockingQueue
        BQ.add("John");
        BQ.add("Tom");
        BQ.add("Clark");
        BQ.add("Kat");

        // find remaining Capacity  of BQ
        // using remainingCapacity() method
        int remainingCapacity
            = BQ.remainingCapacity();

        // print result
        System.out.println("Queue is " + BQ);

        // print head of the queue
        System.out.println("Remaining Capacity of Queue is "
                           + remainingCapacity);
    }
}
Output: 
Queue is [John, Tom, Clark, Kat]
Remaining Capacity of Queue is 3
Program 2: Java 
// Java Program Demonstrate remainingCapacity()
// method of BlockingQueue

import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.BlockingQueue;
public class GFG {

    public void findPeek()
    {
        // define capacity of BlockingQueue
        int capacityOfQueue = 7;

        // create object of BlockingQueue
        BlockingQueue<Employee> BQ
            = new LinkedBlockingQueue<Employee>(
                capacityOfQueue);

        // Add element to BlockingQueue
        Employee emp1
            = new Employee("Ravi", "Tester", "39000");
        Employee emp2
            = new Employee("Sanjeet", "Manager", "98000");

        // Add Employee Objects to BQ
        BQ.add(emp1);
        BQ.add(emp2);

        // add element and find remaining capacity
        // follow same process again
        // until the queue becomes full
        while (BQ.size() != 7) {

            // adding emp2 again and again to queue
            System.out.println(
                "Adding employee is success "
                + BQ.offer(emp2));

            // find remaining capacity of BQ
            // using remainingCapacity() method
            int remain = BQ.remainingCapacity();

            // print remaining capacity  value
            System.out.println(
                "Remaining Capacity of list :"
                + remain);
        }
    }

    // create an Employee Object with name,
    // position and salary as an attribute
    public class Employee {

        public String name;
        public String position;
        public String salary;
        Employee(String name,
                 String position,
                 String salary)
        {
            this.name = name;
            this.position = position;
            this.salary = salary;
        }
        @Override
        public String toString()
        {
            return "Employee [name=" + name
                + ", position="
                + position + ", salary="
                + salary + "]";
        }
    }

    // Main Method
    public static void main(String[] args)
    {
        GFG gfg = new GFG();
        gfg.findPeek();
    }
}
Output: 
Adding employee is success true
Remaining Capacity of list :4
Adding employee is success true
Remaining Capacity of list :3
Adding employee is success true
Remaining Capacity of list :2
Adding employee is success true
Remaining Capacity of list :1
Adding employee is success true
Remaining Capacity of list :0
Reference: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/BlockingQueue.html#remainingCapacity()
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