Stack data Structure

// Java Code for Linked List Implementation 
  
public class StackAsLinkedList { 
  
    StackNode root; 
  
    static class StackNode { 
        int data; 
        StackNode next; 
  
        StackNode(int data) 
        { 
            this.data = data; 
        } 
    } 
  
    public boolean isEmpty() 
    { 
        if (root == null) { 
            return true; 
        } 
        else
            return false; 
    } 
  
    public void push(int data) 
    { 
        StackNode newNode = new StackNode(data); 
  
        if (root == null) { 
            root = newNode; 
        } 
        else { 
            StackNode temp = root; 
            root = newNode; 
            newNode.next = temp; 
        } 
        System.out.println(data + " pushed to stack"); 
    } 
  
    public int pop() 
    { 
        int popped = Integer.MIN_VALUE; 
        if (root == null) { 
            System.out.println("Stack is Empty"); 
        } 
        else { 
            popped = root.data; 
            root = root.next; 
        } 
        return popped; 
    } 
  
    public int peek() 
    { 
        if (root == null) { 
            System.out.println("Stack is empty"); 
            return Integer.MIN_VALUE; 
        } 
        else { 
            return root.data; 
        } 
    } 
  
    public static void main(String[] args) 
    { 
  
        StackAsLinkedList sll = new StackAsLinkedList(); 
  
        sll.push(10); 
        sll.push(20); 
        sll.push(30); 
  
        System.out.println(sll.pop() + " popped from stack"); 
  
        System.out.println("Top element is " + sll.peek()); 
    } 
}