Design patterns Builder Pattern Advanced Builder Pattern With Java 8 Lambda Expression


Example

public class Person {
private final String salutation;
private final String firstName;
private final String middleName;
private final String lastName;
private final String suffix;
private final Address address;
private final boolean isFemale;
private final boolean isEmployed;
private final boolean isHomewOwner;

public Person(String salutation, String firstName, String middleName, String lastName, String suffix, Address address, boolean isFemale, boolean isEmployed, boolean isHomewOwner) {
    this.salutation = salutation;
    this.firstName = firstName;
    this.middleName = middleName;
    this.lastName = lastName;
    this.suffix = suffix;
    this.address = address;
    this.isFemale = isFemale;
    this.isEmployed = isEmployed;
    this.isHomewOwner = isHomewOwner;
 }
}

Old way

public class PersonBuilder {
private String salutation;
private String firstName;
private String middleName;
private String lastName;
private String suffix;
private Address address;
private boolean isFemale;
private boolean isEmployed;
private boolean isHomewOwner;

public PersonBuilder withSalutation(String salutation) {
    this.salutation = salutation;
    return this;
}

public PersonBuilder withFirstName(String firstName) {
    this.firstName = firstName;
    return this;
}

public PersonBuilder withMiddleName(String middleName) {
    this.middleName = middleName;
    return this;
}

public PersonBuilder withLastName(String lastName) {
    this.lastName = lastName;
    return this;
}

public PersonBuilder withSuffix(String suffix) {
    this.suffix = suffix;
    return this;
}

public PersonBuilder withAddress(Address address) {
    this.address = address;
    return this;
}

public PersonBuilder withIsFemale(boolean isFemale) {
    this.isFemale = isFemale;
    return this;
}

public PersonBuilder withIsEmployed(boolean isEmployed) {
    this.isEmployed = isEmployed;
    return this;
}

public PersonBuilder withIsHomewOwner(boolean isHomewOwner) {
    this.isHomewOwner = isHomewOwner;
    return this;
}

public Person createPerson() {
    return new Person(salutation, firstName, middleName, lastName, suffix, address, isFemale, isEmployed, isHomewOwner);
}

Advanced Way:

public class PersonBuilder {
public String salutation;
public String firstName;
public String middleName;
public String lastName;
public String suffix;
public Address address;
public boolean isFemale;
public boolean isEmployed;
public boolean isHomewOwner;

public PersonBuilder with(
        Consumer<PersonBuilder> builderFunction) {
    builderFunction.accept(this);
    return this;
}


public Person createPerson() {
    return new Person(salutation, firstName, middleName,
            lastName, suffix, address, isFemale,
            isEmployed, isHomewOwner);
}

}

Usage:

Person person = new PersonBuilder()
    .with($ -> {
        $.salutation = "Mr.";
        $.firstName = "John";
        $.lastName = "Doe";
        $.isFemale = false;
        $.isHomewOwner = true;
        $.address =
            new PersonBuilder.AddressBuilder()
                .with($_address -> {
                    $_address.city = "Pune";
                    $_address.state = "MH";
                    $_address.pin = "411001";
                }).createAddress();
    })
    .createPerson();

Refer: https://medium.com/beingprofessional/think-functional-advanced-builder-pattern-using-lambda-284714b85ed5#.d9sryx3g9