Set

CollectionFramework/src/Queue/LearnArrayDeque.java

@@ -0,0 +1,29 @@
+package Queue;
+
+import java.util.ArrayDeque;
+
+public class LearnArrayDeque {
+    public static void main(String[] args) {
+        ArrayDeque<Integer> adq = new ArrayDeque<>();
+        // Array Deque can be used to implement stack
+        adq.offer(1);
+        adq.offer(2);
+        adq.offer(3);
+        adq.offerFirst(10);
+        adq.offerLast(20);
+        System.out.println(adq);
+
+        System.out.println(adq.peek());
+        System.out.println(adq.peekFirst());
+        System.out.println(adq.peekLast());
+
+        System.out.println("adq poll: " + adq.poll());
+        System.out.println("adq after poll: " + adq);
+
+        System.out.println("adq poll first: " + adq.pollFirst());
+        System.out.println("adq poll first: " + adq);
+
+        System.out.println("adq poll last: " + adq.pollLast());
+        System.out.println("adq after poll: " + adq);
+    }
+}

CollectionFramework/src/Queue/LearnPriorityQueue.java

@@ -0,0 +1,38 @@
+package Queue;
+
+import java.util.Queue;
+import java.util.Comparator;
+import java.util.PriorityQueue;
+
+public class LearnPriorityQueue {
+    public static void main(String[] args) {
+        // Queue<Integer> pq = new PriorityQueue<>();
+        // pq.offer(40);
+        // pq.offer(12);
+        // pq.offer(24);
+        // pq.offer(36);
+
+        // // under the hood it implements min heap
+        // System.out.println(pq); // pq=[12,36,24,40]
+
+        // pq.poll(); // 12 gets removed
+
+        // System.out.println(pq); // pq=[24, 36, 40]
+
+        // System.out.println(pq.peek());
+
+        /* To get max heap do: */
+        Queue<Integer> pq = new PriorityQueue<>(Comparator.reverseOrder());
+
+        pq.offer(12);
+        pq.offer(24);
+        pq.offer(36);
+        pq.offer(40);
+
+        System.out.println(pq); // pq=[40,36,24,12]
+        System.out.println(pq.poll()); // 40
+        System.out.println(pq.peek()); // 36
+        System.out.println(pq); // pq=[36,12,24]
+
+    }
+}

CollectionFramework/src/Set/LearnSet.java

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+package Set;
+
+import java.util.Set;
+import java.util.HashSet;
+
+public class LearnSet {
+    public static void main(String[] args) {
+        // duplicate elemetn not allowed in set works on hashing
+        // ordering is not defined, everytime you print order is random and new
+        Set<Integer> set = new HashSet<>();
+        set.add(1);
+        set.add(11);
+        set.add(56);
+        set.add(3);
+        set.add(76);
+
+        System.out.println(set);
+
+        set.remove(56);
+        System.out.println(set);
+
+        System.out.println(set.contains(100));
+        System.out.println(set.isEmpty());
+        System.out.println(set.size());
+        set.clear();
+        System.out.println(set);
+    }
+}