DZone
Thanks for visiting DZone today,
Edit Profile
  • Manage Email Subscriptions
  • How to Post to DZone
  • Article Submission Guidelines
Sign Out View Profile
  • Post an Article
  • Manage My Drafts
Over 2 million developers have joined DZone.
Log In / Join
Refcards Trend Reports Events Over 2 million developers have joined DZone. Join Today! Thanks for visiting DZone today,
Edit Profile Manage Email Subscriptions Moderation Admin Console How to Post to DZone Article Submission Guidelines
View Profile
Sign Out
Refcards
Trend Reports
Events
Zones
Culture and Methodologies Agile Career Development Methodologies Team Management
Data Engineering AI/ML Big Data Data Databases IoT
Software Design and Architecture Cloud Architecture Containers Integration Microservices Performance Security
Coding Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
Culture and Methodologies
Agile Career Development Methodologies Team Management
Data Engineering
AI/ML Big Data Data Databases IoT
Software Design and Architecture
Cloud Architecture Containers Integration Microservices Performance Security
Coding
Frameworks Java JavaScript Languages Tools
Testing, Deployment, and Maintenance
Deployment DevOps and CI/CD Maintenance Monitoring and Observability Testing, Tools, and Frameworks
  1. DZone
  2. Coding
  3. Java
  4. Using Traits in Java 8

Using Traits in Java 8

In programming, traits have been around in Scala and PHP a while, but are relatively new through default methods in Java. Here's a quick example on how to use traits in Java 8!

Emil Forslund user avatar by
Emil Forslund
·
Jan. 29, 16 · Tutorial
Like (10)
Save
Tweet
Share
30.20K Views

Join the DZone community and get the full member experience.

Join For Free

In one of my earlier articles I mentioned a programming component called "traits." These constructs have existed for many years in other programming languages like Scala and PHP but have only recently been available through default methods in Java. I will not go into the possibilities of using traits in this article, but I will show you a neat trick that you can use if you ever need to stream over a collection of different objects and separate those that fulfill a number of traits.

Say that you have two noun classes Person and Elephant. There is no reason really why people and elephants should belong to the same super class; elephants are intelligent four-legged creatures and most humans are not. You might still find the two of them in the same computer system and sometimes you even need to store them in the same collection. One way of operating on this collection of various living beings without making them share a common ancestor, (which would totally be just a theory), you can give them similar traits.

Take a look at this interface:

interface HasName extends Document {
    final String NAME = "name";

    default String getName() {
        return get(NAME);
    }

    default void setName(String name) {
        put(NAME, name);
    }
}

Using the Abstract Document Pattern presented earlier, the trait can set and get the attribute "name" from a map. If we now want to iterate over our collection of many living things that might or might not implement our specified traits, we can easily do it like this:


final Set<Object> livingBeings = new HashSet<>();

livingBeings.add(new Person(...));
livingBeings.add(new Person(...));
livingBeings.add(new Elephant(...));

livingBeings.stream()
    .filter(HasName.class::isInstance)
    .filter(HasAge.class::isInstance)
    .filter(HasWeight.class::isInstance)
    .map(p -> (HasName & HasAge & HasHeight) p)
    .forEach(p ->
        System.out.println(
            p.getName() + " is " +
            p.getAge() + " years old and weighs " +
            p.getWeight() + " pounds."
        )
    );

Using the and character (&) we can cast instances that implement all the required traits into a dynamic type, without them sharing an ancestor.

Trait (computer programming) Java (programming language)

Published at DZone with permission of Emil Forslund, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

Popular on DZone

  • Iptables Basic Commands for Novice
  • Distributed SQL: An Alternative to Database Sharding
  • Understanding gRPC Concepts, Use Cases, and Best Practices
  • Using the PostgreSQL Pager With MariaDB Xpand

Comments

Partner Resources

X

ABOUT US

  • About DZone
  • Send feedback
  • Careers
  • Sitemap

ADVERTISE

  • Advertise with DZone

CONTRIBUTE ON DZONE

  • Article Submission Guidelines
  • Become a Contributor
  • Visit the Writers' Zone

LEGAL

  • Terms of Service
  • Privacy Policy

CONTACT US

  • 600 Park Offices Drive
  • Suite 300
  • Durham, NC 27709
  • support@dzone.com
  • +1 (919) 678-0300

Let's be friends: