Create PriorityQueueDemo.java

rahulXbarnwal · web-flow · commit ba98dd804b46 · 2026-03-16T01:14:50.000+05:30
diff --git a/src/learnCollections/PriorityQueueDemo.java b/src/learnCollections/PriorityQueueDemo.java
@@ -0,0 +1,29 @@
+package learnCollections;
+
+import java.util.Comparator;
+import java.util.PriorityQueue;
+
+public class PriorityQueueDemo {
+    public static void main(String[] args) {
+        // Part of the Queue interface
+        // order elements based on their natural ordering (for primitives lowest first)
+        // custom comparator for customized ordering
+        // does not allow null elements
+
+        // min-heap by default
+        PriorityQueue<Integer> pq = new PriorityQueue<>();
+        pq.add(15);
+        pq.add(10);
+        pq.add(30);
+        pq.add(5);
+
+        while(!pq.isEmpty()) {
+            System.out.println(pq.poll()); // 5, 10, 15, 30
+        }
+
+        PriorityQueue<Integer> pq1 = new PriorityQueue<>(Comparator.reverseOrder()); // max-heap
+
+        PriorityQueue<Integer> pq2 = new PriorityQueue<>((a, b) -> a - b); // min-heap using lambda expression
+        PriorityQueue<Integer> pq3 = new PriorityQueue<>((a, b) -> b - a); // max-heap using lambda expression
+    }
+}
