Iterating over a Queue in Java Example


The example in this section 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; /**  * Iterate over Queue with different approaches.  * @author javaguides.net  *  */ public class IterateOverQueueExample { public static void main(String[] args) { Queue<String> elementsQueue = new LinkedList<>(); elementsQueue.add("element1"); elementsQueue.add("element2"); elementsQueue.add("element3"); elementsQueue.add("element4"); System.out.println("=== Iterating over a Queue using Java 8 forEach() ==="); elementsQueue.forEach(name -> { System.out.println(name); }); System.out.println("\n=== Iterating over a Queue using iterator() ==="); Iterator<String> elementQueueIterator = elementsQueue.iterator(); while (elementQueueIterator.hasNext()) { String name = elementQueueIterator.next(); System.out.println(name); } System.out.println("\n=== Iterating over a Queue using iterator() and Java 8 forEachRemaining() ==="); elementQueueIterator = elementsQueue.iterator(); elementQueueIterator.forEachRemaining(name -> { System.out.println(name); }); System.out.println("\n=== Iterating over a Queue using simple for-each loop ==="); for(String name: elementsQueue) { System.out.println(name); } } }
Output:
=== Iterating over a Queue using Java 8 forEach() === element1 element2 element3 element4 === Iterating over a Queue using iterator() === element1 element2 element3 element4 === Iterating over a Queue using iterator() and Java 8 forEachRemaining() === element1 element2 element3 element4 === Iterating over a Queue using simple for-each loop === element1 element2 element3 element4

Reference


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