What is the best practice to repeatedly access a field value of an object in Java and why?

Suppose, I have a class Book.

public class Book {
  private Author author;
  private int pageCount;
  // ... getters and setters
}

And another class Author.

public class Author {
  private String name;
  private int age;
  // ... getters and setters
}

Now, which one of the following is the best way to access the auther name of a book repeatedly from any other class?

void doSomethingA(Book book) {
   print(book.getAuthor().getName());
   publish(book.getAuthor().getName());
}

Or,

void doSomethingB(Book book) {
   Author author = book.getAuthor();
   print(author.getName());
   publish(author.getName());
}

Or,

void doSomethingC(Book book) {
   Author author = book.getAuthor();
   String authorName = author.getName();
   print(authorName);
   publish(authorName);
}

We want to avoid bugs, by making the code easy to read, and removing duplication (because with duplication we may make a change in only opne place when it should have been made in several places)

So none of your options are best. The best is:

void doSomethingC(Book book) {
   String authorName = book.getAuthor().getName();
   print(authorName);
   publish(authorName);
}

Now if we decide that we need to do something to the author name, we can change the code to:

void doSomethingC(Book book) {
   String authorName = massageAuthor(book.getAuthor().getName());
   print(authorName);
   publish(authorName);
}

And the new value is used in both places.