Migrated from old fork (#15626)

core-java-modules/core-java-collections-5/src/main/java/com/baeldung/priorityqueueiterator/Person.java

@@ -0,0 +1,36 @@
+package com.baeldung.priorityqueueiterator;
+
+import java.util.Comparator;
+
+public class Person {
+    String name;
+    int age;
+
+    public Person(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+}
+
+class PersonAgeComparator implements Comparator<Person> {
+    @Override
+    public int compare(Person p1, Person p2) {
+        return p1.age - p2.age; // Ascending order
+    }
+}

core-java-modules/core-java-collections-5/src/main/java/com/baeldung/priorityqueueiterator/PriorityQueueMain.java

@@ -0,0 +1,97 @@
+package com.baeldung.priorityqueueiterator;
+
+import java.util.Iterator;
+import java.util.PriorityQueue;
+
+public class PriorityQueueMain {
+
+    public static void main(String[] args) {
+        showPriorityQueueWithIterator();
+        showCustomOrderingWithIterator();
+        showCustomOrderingWithPoll();
+        useIteratorToCapitalizeNames();
+        showFailFastIteratorBehavior();
+    }
+
+    public static void showPriorityQueueWithIterator() {
+        PriorityQueue<Integer> queue = new PriorityQueue<>();
+        queue.add(3);
+        queue.add(1);
+        queue.add(2);
+
+        Iterator<Integer> iterator = queue.iterator();
+
+        while (iterator.hasNext()) {
+            Integer element = iterator.next();
+            System.out.println(element);
+        }
+    }
+
+    public static void showFailFastIteratorBehavior() {
+        PriorityQueue<Integer> numbers = new PriorityQueue<>();
+        numbers.add(3);
+        numbers.add(1);
+        numbers.add(2);
+
+        Iterator<Integer> iterator = numbers.iterator();
+        numbers.add(4);
+
+        try {
+            while (iterator.hasNext()) {
+                System.out.println(iterator.next());
+            }
+        } catch (java.util.ConcurrentModificationException e) {
+            System.out.println("ConcurrentModificationException occurred during iteration.");
+        }
+    }
+
+    public static void showCustomOrderingWithIterator() {
+        // Creating a PriorityQueue with a custom comparator
+        PriorityQueue<Person> priorityQueue = new PriorityQueue<>(new PersonAgeComparator());
+
+        // Adding persons to the PriorityQueue
+        priorityQueue.add(new Person("Alice", 25));
+        priorityQueue.add(new Person("Bob", 30));
+        priorityQueue.add(new Person("Charlie", 22));
+
+        Iterator<Person> iterator = priorityQueue.iterator();
+
+        while (iterator.hasNext()) {
+            Person person = iterator.next();
+            System.out.println("Name: " + person.name + ", Age: " + person.age);
+        }
+    }
+
+    public static void showCustomOrderingWithPoll() {
+        PriorityQueue<Person> priorityQueue = new PriorityQueue<>(new PersonAgeComparator());
+
+        priorityQueue.add(new Person("Alice", 25));
+        priorityQueue.add(new Person("Bob", 30));
+        priorityQueue.add(new Person("Charlie", 22));
+
+        Iterator<Person> iterator = priorityQueue.iterator();
+
+        while (!priorityQueue.isEmpty()) {
+            Person person = priorityQueue.poll();
+            System.out.println("Name: " + person.name + ", Age: " + person.age);
+        }
+    }
+
+    public static void useIteratorToCapitalizeNames() {
+        PriorityQueue<Person> priorityQueue = new PriorityQueue<>(new PersonAgeComparator());
+
+        priorityQueue.add(new Person("Alice", 25));
+        priorityQueue.add(new Person("Bob", 30));
+        priorityQueue.add(new Person("Charlie", 22));
+
+        Iterator<Person> iterator = priorityQueue.iterator();
+
+        while (iterator.hasNext()) {
+            Person person = iterator.next();
+            person.setName(person.getName()
+                .toUpperCase());
+            System.out.println("Name: " + person.name + ", Age: " + person.age);
+        }
+    }
+
+}