Stack implementation using Linked List in Java

Stack Interface

 package me.farhan.stack;  
 public interface Stack<T>  
 {  
      void push(T t);  
      T pop();  
      T peek();  
      boolean isEmpty();  
 }  

Implementation Class

 package me.farhan.stack;  
 public class StackLinkedImpl<T> implements Stack<T> {  
      class Node  
      {  
           T t;  
           Node next;  
           public Node(T t)   
           {  
                this.t = t;  
                next = null;  
           }  
      }  
      private Node root;  
      public StackLinkedImpl()  
      {  
           root = null;  
      }  
      @Override  
      public synchronized void push(T t)   
      {  
           if(isEmpty())  
           {  
                root = new Node(t);  
                root.next = null;  
           }  
           else  
           {  
                Node node = new Node(t);  
                node.next = root;  
                root = node;  
           }  
      }  
      @Override  
      public synchronized T pop()   
      {  
           if(!isEmpty())  
           {  
                Node temp = root;  
                root = root.next;  
                T t = temp.t;  
                temp = null;  
                return t;  
           }  
           return null;  
      }  
      @Override  
      public synchronized boolean isEmpty()   
      {  
           return root == null;  
      }  
      @Override  
      public synchronized T peek()   
      {  
           if(!isEmpty())  
                return root.t;  
           return null;  
      }  
      public static void main(String[] args)   
      {  
           Stack<Integer> stack = new StackLinkedImpl<>();  
           stack.push(6);  
           stack.push(7);  
           System.out.print(stack.pop());  
      }  
 }