Book Example / Record usage

Author.java

package com.soebes.code.example.book;

public record Author(String name){
  public Author {
    name = NonBlankString.of(name, "author").value();
  }
}

Book.java

package com.soebes.code.example.book;

import java.util.Set;

import static java.util.Objects.requireNonNull;

public record Book(Title title, ISBN isbn, Set<Author> authors) {
  public Book {
    requireNonNull(title, "title is not allowed to be null.");
    requireNonNull(isbn, "isbn is not allowed to be null.");
    requireNonNull(authors, "authors is not allowed to be null.");
    if (authors.isEmpty()) {
      throw new IllegalArgumentException("Authors cannot be empty");
    }
    authors = Set.copyOf(authors);
  }
}

ISBN.java

package com.soebes.code.example.book;

public record ISBN(String isbn) {
  public ISBN {
    isbn = NonBlankString.of(isbn, "ISBN").value();
    if (isbn.length() != 13) {
      throw new IllegalArgumentException("ISBN length must be 13 characters long.");
    }
  }
}

NonBlankString.java

package com.soebes.code.example.book;

record NonBlankString(String value, String name) {
  NonBlankString {
    if (name == null) {
      throw new IllegalStateException("name is null");
    }
    if (value == null) {
      throw new IllegalArgumentException("%s cannot be null".formatted(name));
    }
    if (value.trim().isBlank() || value.isBlank()) {
      throw new IllegalArgumentException("%s cannot be blank".formatted(name));
    }
  }

  static NonBlankString of(String value, String name) {
    return new NonBlankString(value, name);
  }
}

Title.java

package com.soebes.code.example.book;

public record Title(String title) {
  public Title {
    title = NonBlankString.of(title, "title").value();
  }
}