Java sort arraylist of objects by field using comparable

package com.candidjava;

import java.util.ArrayList;
import java.util.Collections;

class Author implements Comparable<Author> {
  String authorname;
  String bookname;
  int bookprice;

  // constructor for author
  Author(String authorname, String bookname, int bookprice) {
    this.authorname = authorname;
    this.bookname = bookname;
    this.bookprice = bookprice;
  }

  // Printing Author in the main
  public String toString() {
    return this.authorname + "    " + this.bookname + "    " + this.bookprice;
  }

  public String getAuthorname() {
    return authorname;
  }

  public void setAuthorname(String authorname) {
    this.authorname = authorname;
  }

  @Override
  public int compareTo(Author o) {

    return this.getAuthorname().compareTo(o.getAuthorname());
  }
}

public class Arraylistsortcomparable {
  public static void main(String[] args) {
    ArrayList<Author> al = new ArrayList<Author>();
    al.add(new Author("Shakespeare", "The Tragedy of Macbeth", 300));
    al.add(new Author("Shakespeare", "The Winters Tale", 350));
    al.add(new Author("Vairamuthu", "Moondram ulaga por", 500));
    al.add(new Author("Dr.A.P.J", "Agni siragugal", 200));
    al.add(new Author("James Gosling", "JAVA Programming Language", 400));
    System.out.println("Unsorted Arraylist");
    for (int i = 0; i < al.size(); i++) {
      System.out.println(al.get(i));
    }
    // Ascending Order
    System.out.println("--------------------------------------------");
    System.out.println("Sorted Array list");
    System.out.println("--------------------------------------------");

    Collections.sort(al);
    for (int i = 0; i < al.size(); i++) {
      System.out.println(al.get(i));
    }
  }
}

OUTPUT

Unsorted Arraylist
Shakespeare    The Tragedy of Macbeth    300
Shakespeare    The Winters Tale    350
Vairamuthu    Moondram ulaga por    500
Dr.A.P.J    Agni siragugal    200
James Gosling    JAVA Programming Language    400
--------------------------------------------
Sorted Array list
--------------------------------------------
Dr.A.P.J    Agni siragugal    200
James Gosling    JAVA Programming Language    400
Shakespeare    The Tragedy of Macbeth    300
Shakespeare    The Winters Tale    350
Vairamuthu    Moondram ulaga por    500