Lecture 7 - slide 17 : 41

class Linkable {
    private Object data;
    private Linkable next;
  
    /** Return a Linkable object with null references in both data and next */ 
    Linkable(){
      data = null;
      next = null;
    }
  
    /** Return a Linkable object with null references in next, and the parameter as data */   
    Linkable(Object data){
      this.data = data;
      this.next = null;
    }
  
    /** Return a Linkable object with first parameter as data and second parameter as next */
    Linkable(Object data, Linkable next){
      this.data = data;
      this.next = next;
    }
  
    /** Return the data of this Linkable object */
    Object data(){
      return (data);
    }
  
    /** Return the reference to the next Linkable */
    Linkable next(){
      return (next);
    }
  
    /** Set the data field of this Linkable object */
    void setData(Object data){
      this.data = data;
    }
  
    /** Set the next field of this Linkable object */
    void setNext(Linkable next){
      this.next = next;
    }
  
  } // end Linkable