Iterating over a Queue in Java Example

Java Queue Examples

---

• Creating a Queue and Performing basic operations like Enqueue and Dequeue
• Iterating over a Queue in Java Example
• Java PriorityQueue Example
• Java Deque and ArrayDeque Examples
• Iterating over a Queue in Java Example
• Java Queue isEmpty(), size(), element() and peek() Example
• Java Queue Interface Example
• Java Priority Queue of User Defined Objects Example
• Java Create a Priority Queue with a Custom Comparator
• Create a Priority Queue in Java Example

The example shows various ways of iterating over a Queue:

• Iterate over a Queue using Java 8 forEach() method.

• Iterate over a Queue using iterator().

• Iterate over a Queue using iterator() and Java 8 forEachRemaining() method.

• Iterate over a Queue using a simple for-each loop.

The iteration order in a Queue is the same as the insertion order.

import java.util.Iterator;
import java.util.LinkedList;
import java.util.Queue;

public class IterateOverQueueExample {
    public static void main(String[] args) {
        Queue<String> waitingQueue = new LinkedList<>();

        waitingQueue.add("John");
        waitingQueue.add("Brad");
        waitingQueue.add("Angelina");
        waitingQueue.add("Julia");

        System.out.println("=== Iterating over a Queue using Java 8 forEach() ===");
        waitingQueue.forEach(name -> {
            System.out.println(name);
        });

        System.out.println("\n=== Iterating over a Queue using iterator() ===");
        Iterator<String> waitingQueueIterator = waitingQueue.iterator();
        while (waitingQueueIterator.hasNext()) {
            String name = waitingQueueIterator.next();
            System.out.println(name);
        }

        System.out.println("\n=== Iterating over a Queue using iterator() and Java 8 forEachRemaining() ===");
        waitingQueueIterator = waitingQueue.iterator();
        waitingQueueIterator.forEachRemaining(name -> {
            System.out.println(name);
        });

        System.out.println("\n=== Iterating over a Queue using simple for-each loop ===");
        for(String name: waitingQueue) {
            System.out.println(name);
        }
    }
}

# Output
=== Iterating over a Queue using Java 8 forEach() ===
John
Brad
Angelina
Julia

=== Iterating over a Queue using iterator() ===
John
Brad
Angelina
Julia

=== Iterating over a Queue using iterator() and Java 8 forEachRemaining() ===
John
Brad
Angelina
Julia

=== Iterating over a Queue using simple for-each loop ===
John
Brad
Angelina
Julia