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 Video Library
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
View Events Video Library
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

Integrating PostgreSQL Databases with ANF: Join this workshop to learn how to create a PostgreSQL server using Instaclustr’s managed service

Mobile Database Essentials: Assess data needs, storage requirements, and more when leveraging databases for cloud and edge applications.

Monitoring and Observability for LLMs: Datadog and Google Cloud discuss how to achieve optimal AI model performance.

Automated Testing: The latest on architecture, TDD, and the benefits of AI and low-code tools.

Related

  • How the Strangler Fig Approach Can Revitalize Complex Applications
  • Design Pattern: What You Need to Know to Improve Your Code Effectively
  • Strategy vs. Factory Design Patterns in Java
  • The Open/Closed Principle and Strategy Pattern

Trending

  • Auto-Scaling DynamoDB Streams Applications on Kubernetes
  • Docker and Kubernetes Transforming Modern Deployment
  • Scalable Rate Limiting in Java With Code Examples: Managing Multiple Instances
  • Modern Data Backup Strategies for Safeguarding Your Information

Strategy Pattern Implemented as an Enum Using Lambdas

Learn how to implement strategy patterns by developing a calculator in Java.

Alex Theedom user avatar by
Alex Theedom
·
Jul. 28, 15 · Tutorial
Like (7)
Save
Tweet
Share
21.40K Views

Join the DZone community and get the full member experience.

Join For Free

In this post I would like to show how the strategy pattern can be implemented as an enum with lambdas.

The Strategy Pattern is one of the Gang of Four design patterns published in their book: Elements of Reusable Object-Oriented Software. The intent of the strategy pattern is:

Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.

We will develop a simple calculator where the strategies are basic arithmetic operations. We start with an interface that defines a single abstract method.

@FunctionalInterface
public interface OperationStrategy {
    T compute(T x, T y);
}


We now implement each arithmetic operation using a lambda expresion.

public enum Operation implements OperationStrategy {

    ADD((x, y) -> x + y),
    SUBTRACT((x, y) -> x - y),
    MULTIPLY((x, y) -> x * y),
    DIVIDE((x, y) -> x / y),
    MAX(Double::max);

    private OperationStrategy operationStrategy;

    Operation(final OperationStrategy operationStrategy) {
        this.operationStrategy = operationStrategy;
    }

    @Override
    public Double compute(Double x, Double y) {
        return operationStrategy.compute(x, y);
    }
}


A series of tests prove that it works.

@RunWith(MockitoJUnitRunner.class)
public class OperationStrategyTest {

    @Test
    public void shouldAddTwoNumbers() {
        assertThat(Operation.ADD.compute(5d, 5d)).isEqualTo(new Double(10));
    }

    @Test
    public void shouldSubtractTwoNumbers() {
        assertThat(Operation.SUBTRACT.compute(10d, 5d)).isEqualTo(new Double(5d));
    }

    @Test
    public void shouldMultiplyTwoNumbers() {
        assertThat(Operation.MULTIPLY.compute(5d, 5d)).isEqualTo(new Double(25));
    }

    @Test
    public void shouldDivideTwoNumbers() {
        assertThat(Operation.DIVIDE.compute(10d, 2d)).isEqualTo(new Double(5d));
    }

    @Test
    public void shouldDetermineMaximumOfTwoNumbers() {
        assertThat(Operation.MAX.compute(10d, 5d)).isEqualTo(new Double(10d));
    }
}


The use of lambdas as strategies reduces boilerplate code quite substantially, though it would not be correct to use lambdas if the strategy is complex and requires a lot of code. It would become cumbersome.

A git repository of this code is available here.

Strategy pattern

Published at DZone with permission of Alex Theedom, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

Related

  • How the Strangler Fig Approach Can Revitalize Complex Applications
  • Design Pattern: What You Need to Know to Improve Your Code Effectively
  • Strategy vs. Factory Design Patterns in Java
  • The Open/Closed Principle and Strategy Pattern

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

  • 3343 Perimeter Hill Drive
  • Suite 100
  • Nashville, TN 37211
  • support@dzone.com

Let's be friends: