Queue-Data structure using Java(without using library)

Queue.java

/**
  * Implementation of Queue using Java
  * @author Al- Imran Ahmed
  */ 
public class Queue<T>{
  Node font = null;
  Node back = null;
  private class Node{
    T item;
    Node next;
  }
    
  /**
    * Remove an element from the end of the queue
    * @return T
    * public T dequeue(){ return null; } ;stub
    */
  public T dequeue(){
    if(isEmpty()){
      return null; 
    }
    T item = font.item;
    if(font == back){
      back = back.next;
    }
    font = font.next;
    return item;
  }
    
  /**
    * Insert an element at the beginning of the queue
    * @param T
    * public void enqueue(T item){ } ; stub;
    */ 
  public void enqueue(T item){
    Node oldback = back;
    back = new Node();
    back.item = item;
    if(isEmpty()){
      font = back;
    }else{
      oldback.next = back;
    }
  }
    
  /**
    * Check whether the queue is empty or not
    * @return boolean 
    * public boolean isEmpty(){ return false; } ;stub
    */ 
  public boolean isEmpty(){
    return font == null;
  }
}

Client.java

/**
  * Client to Test Queue.java
  * @author Al- Imran Ahmed
  * Enqueue each value but dequeue when '-' entered
  * java Client < input.txt
  */

import java.util.Scanner;
public class Client{
  //Client method 
  public static void main(String[] CHAND){
    
    //Create an instance of stack 
    Queue<String> queue = new Queue<String>();
    Scanner input = new Scanner(System.in);
    String s;
    System.out.println("Output: ");
    while(input.hasNext()){
      s = input.next();
      if(s.equals("-")){
        System.out.print(queue.dequeue()+" ");
      }else{
        queue.enqueue(s);
      }
    }
    System.out.println();
  }
}