Stack Queue Iteration Examples

Author: Rajeev Kumar Singh

java-queue-examples/src/IterateOverQueueExample.java

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+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);
+        }
+    }
+}

java-stack-examples/src/IterateOverStackExample.java

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+import java.util.Iterator;
+import java.util.ListIterator;
+import java.util.Stack;
+
+public class IterateOverStackExample {
+    public static void main(String[] args) {
+        Stack<String> stackOfPlates = new Stack<>();
+
+        stackOfPlates.add("Plate 1");
+        stackOfPlates.add("Plate 2");
+        stackOfPlates.add("Plate 3");
+        stackOfPlates.add("Plate 4");
+
+        System.out.println("=== Iterate over a Stack using Java 8 forEach() method ===");
+        stackOfPlates.forEach(plate -> {
+            System.out.println(plate);
+        });
+
+        System.out.println("\n=== Iterate over a Stack using iterator() ===");
+        Iterator<String> platesIterator = stackOfPlates.iterator();
+        while (platesIterator.hasNext()) {
+            String plate = platesIterator.next();
+            System.out.println(plate);
+        }
+
+        System.out.println("\n=== Iterate over a Stack using iterator() and Java 8 forEachRemaining() method ===");
+        platesIterator = stackOfPlates.iterator();
+        while (platesIterator.hasNext()) {
+            String plate = platesIterator.next();
+            System.out.println(plate);
+        }
+
+
+        System.out.println("\n=== Iterate over a Stack from TOP to BOTTOM using listIterator() ===");
+        // ListIterator allows you to traverse in both forward and backward directions.
+        // We'll start from the top of the stack and traverse backwards.
+        ListIterator<String> platesListIterator = stackOfPlates.listIterator(stackOfPlates.size());
+        while (platesListIterator.hasPrevious()) {
+            String plate = platesListIterator.previous();
+            System.out.println(plate);
+        }
+    }
+}