BlockingQueue remainingCapacity() method in Java with examples

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 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 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()