LinkedTransferQueue in Java
Last Updated :
11 Jul, 2025
In Java, the LinkedTransferQueue is a part of the java.util.concurrent package and implements the TransferQueue. It is specifically designed for handling concurrent data transfers. It is a non-blocking, thread-safe, unbounded queue that supports both producer-consumer and transfer operations, making it suitable for high-performance, multi-threaded applications.
- Most of its methods are non-blocking, offering thread-safe operations without locking.
- It can grow dynamically to accommodate more elements without any predefined limit.
- Optimized for high-throughput and low-latency transfers in multi-threaded environments.
- The transfer() method allows producers to send elements directly to consumers.
Example: This example, demonstrates how to add elements to a LinkedTransferQueue and then retrieve and print them using poll() until the queue is empty.
Java
// Java Program to demonstrate the
// working of LinkedTransferQueue
import java.util.concurrent.*;
public class Geeks {
public static void main(String[] args) {
// Create a LinkedTransferQueue
LinkedTransferQueue<String> q = new LinkedTransferQueue<>();
// Add some elements to the queue
q.add("1");
q.add("2");
q.add("3");
// Print the elements of the queue
System.out.println("LinkedTransferQueue is: ");
while (!q.isEmpty()) {
System.out.print(q.poll() + " ");
}
}
}
OutputLinkedTransferQueue is:
1 2 3
LinkedTransferQueue Hierarchy
Declaration of LinkedTransferQueue
In Java, the declaration of LinkedTransferQueue can be done as:
LinkedTransferQueue<Type> queue = new LinkedTransferQueue<>();
Note: Here, the Type is the type of element the queue will store(e.g String, Integer)
Constructors
Constructor | Description |
|---|
LinkedTransferQueue() | This constructor is used to construct an empty queue. |
LinkedTransferQueue(Collection<E> c) | This constructor is used to construct a queue with the elements of the Collection passed as the parameter. |
Example 1: This example demonstrates how to create a LinkedTransferQueue add elements to it, and then copy the elements to another LinkedTransferQueue.
Java
// Java Program to demonstrates how
// to copy elements to another LinkedTransferQueue
import java.util.concurrent.LinkedTransferQueue;
public class Geeks {
public static void main(String[] args) {
// Create object of LinkedTransferQueue
LinkedTransferQueue<Integer> l = new LinkedTransferQueue<Integer>();
// Add numbers to the LinkedTransferQueue
l.add(1);
l.add(2);
l.add(3);
l.add(4);
// Print Queue 1
System.out.println("LinkedTransferQueue1: " + l);
// Create a new LinkedTransferQueue
// with the elements from the first queue
LinkedTransferQueue<Integer> l2 = new LinkedTransferQueue<Integer>(l);
// Print Queue 2
System.out.println("LinkedTransferQueue2: " + l2);
}
}
OutputLinkedTransferQueue1: [1, 2, 3, 4]
LinkedTransferQueue2: [1, 2, 3, 4]
Example 2: This example demonstrates how use various methods of LinkedTransferQueue.
Java
// Java Program to demosntrate the
// working of add(), poll() and size() method
import java.util.concurrent.LinkedTransferQueue;
import java.util.*;
public class Geeks {
public static void main(String[] args)
throws InterruptedException
{
// create object of LinkedTransferQueue
LinkedTransferQueue<Integer> l
= new LinkedTransferQueue<Integer>();
// Add numbers to end of LinkedTransferQueue
// using add() method
l.add(10);
l.add(20);
l.add(30);
l.add(40);
// prints the Queue
System.out.println("LinkedTransferQueue: " + l);
// prints the size of Queue after removal
// using size() method
System.out.println("Size of LinkedTransferQueue: "
+ l.size());
// removes the front element and prints it
// using poll() method
System.out.println("First element: " + l.poll());
// prints the Queue
System.out.println("Linked Transfer Queue: " + l);
System.out.println("Size of LinkedTransferQueue: "
+ l.size());
}
}
OutputLinkedTransferQueue: [10, 20, 30, 40]
Size of LinkedTransferQueue: 4
First element: 10
Linked Transfer Queue: [20, 30, 40]
Size of LinkedTransferQueue: 3
Performing Various Operations on LinkedTransferQueue
1. Adding Elements: We can use various like add(), put(), offer() method to insert element in a LinkedTransferQueue without waiting for other thread. The transfer() method waits until another thread is ready to take the element.
Example: This example demonstrates adding, offering, and transferring elements in a LinkedTransferQueue including blocking operations like put() and transfer() across thread.
Java
// Java Program to demonstrate adding
// elements to LinkedTransferQueue
import java.util.concurrent.*;
class Geeks {
public static void main(String[] args)
{
// Initializing the queue
LinkedTransferQueue<Integer> q
= new LinkedTransferQueue<Integer>();
// Adding elements to this queue
for (int i = 10; i <= 14; i++)
q.add(i);
// Add the element using offer() method
System.out.println("adding 15 "
+ q.offer(15, 5, TimeUnit.SECONDS));
// Adding elements to this queue
for (int i = 16; i <= 20; i++)
q.put(i);
// Printing the elements of the queue
System.out.println(
"The elements in the queue are:");
for (Integer i : q)
System.out.print(i + " ");
System.out.println();
// create another queue to demonstrate transfer
// method
LinkedTransferQueue<String> g
= new LinkedTransferQueue<String>();
new Thread(new Runnable() {
public void run()
{
try {
System.out.println("Transferring"
+ " an element");
// Transfer a String element
// using transfer() method
g.transfer("is a computer"
+ " science portal.");
System.out.println(
"Element "
+ "transfer is complete");
}
catch (InterruptedException e1) {
System.out.println(e1);
}
catch (NullPointerException e2) {
System.out.println(e2);
}
}
})
.start();
try {
// Get the transferred element
System.out.println("Geeks for Geeks "
+ g.take());
}
catch (Exception e) {
System.out.println(e);
}
}
}
Outputadding 15 true
The elements in the queue are:
10 11 12 13 14 15 16 17 18 19 20
Transferring an element
Element transfer is complete
Geeks for Geeks is a computer science portal.
2. Remove Elements: We can use remove() method to remove an element if it is present in the queue.
Example: This example demonstrates how to remove specific element from the queue using remove() method.
Java
// Java Program to demonstrate removing
// elements of LinkedTransferQueue
import java.util.concurrent.LinkedTransferQueue;
class Geeks {
public static void main(String[] args)
{
// Initializing the q
LinkedTransferQueue<Integer> q
= new LinkedTransferQueue<Integer>();
// Adding elements to this q
for (int i = 1; i <= 5; i++)
q.add(i);
// Printing the elements of the q
System.out.println(
"The elements in the Queue are:");
for (Integer i : q)
System.out.print(i + " ");
// remove() method will remove the specified
// element from the q
q.remove(1);
q.remove(5);
// Printing the elements of the q
System.out.println(
"\nRemaining elements in Queue are : ");
for (Integer i : q)
System.out.print(i + " ");
}
}
OutputThe elements in the Queue are:
1 2 3 4 5
Remaining elements in Queue are :
2 3 4
3. Iterating Elements: We can use the iterator() method of LinkedTransferQueue which return an iterator that allows traversing through the elements of the queue.
Example: This example demonstrates iterating over the elements of a LinkedTransferQueue using an iterator.
Java
// Java Program to demonstrate iterating
// over LinkedTransferQueue
import java.util.Iterator;
import java.util.concurrent.LinkedTransferQueue;
class Geeks {
public static void main(String[] args)
{
// Initializing the queue
LinkedTransferQueue<String> q
= new LinkedTransferQueue<String>();
// Adding elements to this queue
q.add("GeeksForGeeks");
q.add("is");
q.add("fun!!");
// Returns an iterator over the elements
Iterator<String> i = q.iterator();
// Printing the elements of the queue
while (i.hasNext())
System.out.print(i.next() + " ");
}
}
OutputGeeksForGeeks is fun!!
Methods
Methods | Description |
|---|
| add(E e) | Inserts the specified element at the tail of this queue. |
| contains(Object o) | Returns true if this queue contains the specified element. |
| drainTo(Collection<? super E> c) | Removes all available elements from this queue and adds them to the given collection. |
| drainTo(Collection<? super E> c, int maxElements) | Removes at most the given number of available elements from this queue and adds them to the given collection. |
| forEach(Consumer<? super E> action) | Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception. |
| isEmpty() | Returns true if this queue contains no elements. |
| iterator() | Returns an iterator over the elements in this queue in proper sequence. |
| offer(E e) | Inserts the specified element at the tail of this queue. |
| offer(E e, long timeout, TimeUnit unit) | Inserts the specified element at the tail of this queue. |
| put(E e) | Inserts the specified element at the tail of this queue. |
| remainingCapacity() | Always returns Integer.MAX_VALUE because a LinkedTransferQueue is not capacity constrained. |
| remove(Object o) | Removes a single instance of the specified element from this queue, if it is present. |
| removeAll(Collection<?> c) | Removes all of this collection’s elements that are also contained in the specified collection (optional operation). |
| removeIf(Predicate<? super E> filter) | Removes all of the elements of this collection that satisfy the given predicate. |
| retainAll(Collection<?> c) | Retains only the elements in this collection that are contained in the specified collection (optional operation). |
| size() | Returns the number of elements in this queue. |
| spliterator() | Returns a Spliterator over the elements in this queue. |
| toArray() | Returns an array containing all of the elements in this queue, in proper sequence. |
| toArray(T[] a) | Returns an array containing all of the elements in this queue, in proper sequence; the runtime type of the returned array is that of the specified array. |
| transfer(E e) | Transfers the element to a consumer, waiting if necessary to do so. |
| tryTransfer(E e) | Transfers the element to a waiting consumer immediately, if possible. |
| tryTransfer(E e, long timeout, TimeUnit unit) | Transfers the element to a consumer if it is possible to do so before the timeout elapses. |
Methods Declared in Class java.util.AbstractQueue
Methods Declared in Class java.util.AbstractCollection
METHOD | DESCRIPTION |
|---|
| containsAll(Collection<?> c) | Returns true if this collection contains all of the elements in the specified collection. |
| toString() | Returns a string representation of this collection. |
Methods Declared in Interface java.util.concurrent.BlockingQueue
METHOD | DESCRIPTION |
|---|
| poll(long timeout, TimeUnit unit) | Retrieves and removes the head of this queue, waiting up to the specified wait time if necessary for an element to become available. |
| take() | Retrieves and removes the head of this queue, waiting if necessary until an element becomes available. |
Methods Declared in Interface java.util.Collection
METHOD | DESCRIPTION |
|---|
| addAll(Collection<? extends E> c) | Adds all of the elements in the specified collection to this collection (optional operation). |
| clear() | Removes all of the elements from this collection (optional operation). |
| containsAll(Collection<?> c) | Returns true if this collection contains all of the elements in the specified collection. |
| equals(Object o) | Compares the specified object with this collection for equality. |
| hashCode() | Returns the hash code value for this collection. |
| parallelStream() | Returns a possibly parallel Stream with this collection as its source. |
| stream() | Returns a sequential Stream with this collection as its source. |
| toArray(IntFunction<T[]> generator) | Returns an array containing all of the elements in this collection, using the provided generator function to allocate the returned array. |
Methods Declared in Interface java.util.Queue
METHOD | DESCRIPTION |
|---|
| element() | Retrieves, but does not remove, the head of this queue. |
| peek() | Retrieves, but does not remove, the head of this queue, or returns null if this queue is empty. |
| poll() | Retrieves and removes the head of this queue, or returns null if this queue is empty. |
| remove() | Retrieves and removes the head of this queue. |
Methods Declared in Interface java.util.concurrent.TransferQueue
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