feat:Added Stack Implementation Using LinkedList

Author: tarandeepsingh-wd

src/main/java/com/thealgorithms/stacks/StackUsingLinkedList.java

@@ -0,0 +1,89 @@
+package com.thealgorithms.stacks;
+
+class Node<T> {
+    T data;
+    Node<T> next;
+
+    public Node(T data) {
+        this.data = data;
+        this.next = null;
+    }
+}
+
+public class StackUsingLinkedList<T> {
+    private Node<T> top;
+    private int size;
+
+    public StackUsingLinkedList() {
+        top = null;
+        size = 0;
+    }
+
+    // Push operation
+    public void push(T data) {
+        Node<T> temp = new Node<>(data);
+        temp.next = top;
+        top = temp;
+        size++;
+    }
+
+    // Pop operation
+    public T pop() {
+        if (top == null) {
+            throw new RuntimeException("Stack Underflow");
+        }
+        T value = top.data;
+        Node<T> temp = top;
+        top = top.next;
+        temp.next = null; // help GC
+        size--;
+        return value;
+    }
+
+    // Peek operation
+    public T peek() {
+        if (top == null) {
+            throw new RuntimeException("Stack is empty");
+        }
+        return top.data;
+    }
+
+    // Size operation (O(1))
+    public int size() {
+        return size;
+    }
+    public boolean isEmpty() {
+        return size == 0;
+    }
+}
+class demo{
+    public static void main(String[] args) {
+        StackUsingLinkedList<Integer> stack = new StackUsingLinkedList<>();
+
+        System.out.println("Is stack empty? " + stack.isEmpty());
+        System.out.println("Initial size: " + stack.size());
+
+
+        stack.push(10);
+        stack.push(20);
+        stack.push(30);
+
+        System.out.println("After pushes:");
+        System.out.println("Top element: " + stack.peek()); // 30
+        System.out.println("Size: " + stack.size());        // 3
+
+        // Pop elements
+        System.out.println("Popped: " + stack.pop()); // 30
+        System.out.println("Popped: " + stack.pop()); // 20
+
+        System.out.println("After pops:");
+        System.out.println("Top element: " + stack.peek()); // 10
+        System.out.println("Size: " + stack.size());        // 1
+
+        System.out.println("Is stack empty? " + stack.isEmpty());
+
+
+        stack.pop();
+        System.out.println("Is stack empty after final pop? " + stack.isEmpty());
+    }
+}