@FreeBuilder

Automatic generation of the Builder pattern for Java

Quick Start

Want a Builder API without the hassle? In your file, add: 
dependencies {
  annotationProcessor 'org.inferred:freebuilder:<current version>'
  compileOnly 'org.inferred:freebuilder:<current version>'
}
Now just annotate, extend and go!
import org.inferred.freebuilder.FreeBuilder;

@FreeBuilder
public interfaceYou can also use an abstract class if you want to add private methods. Person {
  /** Returns the person's full (English) name. */
  String name();
  /** Returns the person's age in years, rounded down. */
  int age();

  class Builder extends Person_BuilderThe Person_Builder class is generated by FreeBuilder. {}
}

Person bob = new Person.Builder().name("Bob").age(23).build();

For a complete feature list, extensive README, and issue tracker, please see the project page on GitHub.

Features

FreeBuilder is packed with things like...

Collections support
@FreeBuilder
interface TopOfThePops {
  /** Artists who've released Number 1 hits. */
  Set<String> artists();
  /** Best album each year. */
  Map<Integer, String> albums();

  class Builder extends TopOfThePops_Builder {}
}

new TopOfThePops.Builder()
    .addArtists("Michael Jackson", "Billy Bragg")
    .putAllAlbums(albumsByYear)
    .build();
Guava collections support
@FreeBuilder
interface BookShop {
  /** Shop assistants. */
  Multiset<String> assistants();
  /** Books by category. */
  Multimap<String, String> books();

  class Builder extends BookShop_Builder {}
}

new BookShop.Builder()
    .addAssistants("Bill", "Bob")
    .putAllBooks("Science Fiction", asList("I, Robot", "Cyteen"))
    .build();
Jackson support (just one line!)
@FreeBuilder
@JsonDeserialize(builder = Person.Builder.class)
public interface Person {
  /** Returns the person's full (English) name. */
  String name();
  /** Returns the person's age in years, rounded down. */
  int age();

  class Builder extends Person_Builder {}
}

Person person = new ObjectMapper().readValue(
    "{\"name\":\"Bob\", \"age\":23}", Person.class);
GWT support
@FreeBuilder
@GwtCompatible(serializable = true)
public interface Person extends Serializable {
  /** Returns the person's full (English) name. */
  String name();
  /** Returns the person's age in years, rounded down. */
  int age();

  class Builder extends Person_Builder {}
}

RPC.encodeResponseForSuccess(someMethod, person);
Don't just build, modify!
BookShop bookshop = BookShop.Builder
    .fromThe static from method turns a data object back into a Builder.(acquiredBookshop)
    .removeAssistants("Terry")
    .mutateBooksThe modify and mutate methods let you pass in a lambda, for more readable code,
or to access collection methods not available on the builder API.(books -> {
      Collection<String> sciFi = books.removeAll("Science Fiction")This modifies the books collection on the builder.;
      books.putAll("sci-fi", sciFi);
    })
    .mergeFromThe mergeFrom method combines collections.(existingBookshop)
    .build();
Keep your tests robust with partials
// This code doesn't need to care about the ins-and-outs
// of ISBN compliance (when we get around to implementing
// it!), nor does it need any of the other fields we're
// planning on adding to Book, so rather than have to fix
// this test every time we modify Book, just pass in a
// partial.
Book book = new Book.Builder()
    .name("I, Robot")
    .isbn("Some ISBN")
    .buildPartial();  // Skips validation

// Whoops! Throws UnsupportedOperationException.
book.publicationDate();

For a complete feature list, extensive README, and issue tracker, please see the project page on GitHub.