Convert from a Constructor to a Builder

[Daniel Afonso]

Hi have the following code:

public class PaperInformation implements Serializable {

	private static final long serialVersionUID = -3533611347526231969L;

	@Id
	@GeneratedValue
        @Column(name = "ID")
	private transient int id;

	@Column(name = "NAME")
	private String name;

	@Column(name = "ADDRESS")
	private String address;

	@Column(name = "ZIPCODE")
	private String zipCode;

	@Column(name = "CITY")
	private String city;

	@Column(name = "COUNTRY")
	private String country;

	@Column(name = "PHONENUMBER")
	private String phoneNumber;

	@Column(name = "EMAIL")
	private String email;

	@Column(name = "NIB")
	private transient String nib;
	
	@Column(name = "IBAN")
	private transient String iban;
	
	@Column(name = "BIC")
	private transient String bic;

	@Column(name = "LOGOIMAGE")
	private String logoImage;

	@Column(name = "IMGBANNER")
	private String imgBanner;

	@Column(name = "IMAGEBACKGROUND")
	private String imageBackground;

	@Column(name = "THEME")
	private String theme;
	public PaperInformation(
             final int id, final String name, final String address,
             final String imgBanner, final String city, final String country,
             final String phoneNumber, final String email,
             final String logoImage, final String imageBackground,
             final String zipCode, final String nib,
             final String iban, final String bic){
		this.idPaperInfo = id;
		this.name = name;
		this.imgBanner = imgBanner;
		this.address = address;
		this.city = city;
		this.country = country;
		this.phoneNumber = phoneNumber;
		this.email = email;
		this.logoImage = logoImage;
		this.zipCode = zipCode;
		this.nib = nib;
		this.iban = iban;
		this.bic= bic;
		this.imageBackground = imageBackground;
	}

How would I convert this to a Builder. I'm pretty new on this.

[Campbell Ritchie]

Several ways to do it. You will have to consider whether you want to permit any changes to those fields. You should also consider whether it is wise to have so many parameters for your constructor; for one thing it makes the code hard to read, and I had to insert some line breaks.

public class Address
{
   private String number; // House number or name
   private String street;
   private String locality;
   private String town;
   private String county;
   private String postCode;

   private Address()
   {
      number = "";
      street = "";
      locality = "";
      town = "";
      county = "";
      postCode "";
   }

   public String getNumber()
   {
       return number;
   }
/*
 * Other get methods similarly. Strings are immutable, so those get methods
 * don't permit changes to the class' state. Set methods not implemented.
 * Usual hashCode equals and toString methods.
 */
   private static Address getBasicAddress(String town, String postCode)
   {
       if (town == null || postCode == null)
       {
           throw new NullPointerException("Town and postCode must not be null.");
       }
       Address a = new Address();
       a.town = town;
       a.postCode = postCode;
       return a;
   }

   public static Address getAddressWithoutStreetAndCounty(
           String number, String locality, String town, String postCode)
   {
       address a = getBasicAddress(town, postCode);
       a.locality = locality == null ? "" : locality;
       a.number = number == null ? "" : number;
       return a;
   }
}

That is one way to do it. You can set up lots of methods for different combinations.

In that case they all have the structure Address a = getBasicAddress(...); ... return a;

The getBasicAddress method requires postCode and town be not null, and other null fields are changed to "", so there are no nulls.

You can do validation of the fields in those methods, eg with a regex for post codes.

There are other ways to do it, too.