Java Language Fluent programming style


Example

In fluent programming style you return this from fluent (setter) methods that would return nothing in non-fluent programming style.

This allows you to chain the different method calls which makes your code shorter and easier to handle for the developers.

Consider this non-fluent code:

public class Person {
  private  String firstName;
  private String lastName;

  public String getFirstName() {
    return firstName;
  }

  public void setFirstName(String firstName) {
    this.firstName = firstName;
  }

  public String getLastName() {
    return lastName;
  }

  public void setLastName(String lastName) {
    this.lastName = lastName;
  }

  public String whoAreYou() {
    return "I am " + firstName + " " + lastName;
  }

  public static void main(String[] args) {
    Person person = new Person();
    person.setFirstName("John");
    person.setLastName("Doe");
    System.out.println(person.whoAreYou());
  }
}

As the setter methods don't return anything, we need 4 instructions in the mainmethod to instantiate a Person with some data and print it. With a fluent style this code can be changed to:

public class Person {
  private  String firstName;
  private String lastName;

  public String getFirstName() {
    return firstName;
  }

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

  public String getLastName() {
    return lastName;
  }

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

  public String whoAreYou() {
    return "I am " + firstName + " " + lastName;
  }

  public static void main(String[] args) {
    System.out.println(new Person().withFirstName("John")
      .withLastName("Doe").whoAreYou());
  }
}

The idea is to always return some object to enable building of a method call chain and to use method names which reflect natural speaking. This fluent style makes the code more readable.