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

  • Streamlining Your Workflow With the Jenkins HTTP Request Plugin: A Guide to Replacing CURL in Scripts
  • Why "Polyglot Programming" or "Do It Yourself Programming Languages" or "Language Oriented Programming" sucks?
  • Groovy Database Resource Handling
  • Containerize Gradle Apps and Deploy to Kubernetes With JKube Kubernetes Gradle Plugin

Trending

  • CAN Bus: How It Works, Pros and Cons, and Fast Local Processing Tutorial
  • Java Parallel GC Tuning
  • Unlocking Opportunities: The Advantages of Certifications for Software Engineers
  • Creating a High-Performance DevOps Toolchain
  1. DZone
  2. Coding
  3. Languages
  4. Groovy Goodness: Closure as a Class

Groovy Goodness: Closure as a Class

Hubert Klein Ikkink user avatar by
Hubert Klein Ikkink
·
Oct. 17, 14 · Interview
Like (0)
Save
Tweet
Share
7.86K Views

Join the DZone community and get the full member experience.

Join For Free

When we write Groovy code there is a big change we also write some closures. If we are working with collections for example and use the each,collect or find methods we use closures as arguments for these methods. We can assign closures to variables and use the variable name to reference to closure. But we can also create a subclass of the Closure class to implement a closure. Then we use an instance of the new closure class wherever a closure can be used.

To write a closure as a class we must subclass Closure and implement a method with the name doCall. The method can accept arbitrary arguments and the return type can be defined by us. So we are not overriding a method doCall from the superclass Closure. But Groovy will look for a method with the name doCall to execute the closure logic and internally use methods from the Closure superclass.

In the following sample we write a very simple closure as a class to check if an object is a number. Then we use an instance of the class with thefindAll method for a collection of objects:

class IsNumber extends Closure<Boolean> /http://mrhaki.blogspot.ie/2014/10/groovy-goodness-closure-as-class.html* return type for closure as generic type */ {

    IsNumber() {
        super(null)
    }

    /**
     * Implementation of closure.
     */
    Boolean doCall(final Object value) {
        // Check if value is a number, if so
        // return true, otherwise false.
        value in Number
    }

}

def list = ['a', 100, 'Groovy', 1, 8, 42.0, true]

def numbers = list.findAll(new IsNumber())

assert numbers == [100, 1, 8, 42.0]

Code written with Groovy 2.3.7.

Groovy (programming language)

Published at DZone with permission of Hubert Klein Ikkink, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

Related

  • Streamlining Your Workflow With the Jenkins HTTP Request Plugin: A Guide to Replacing CURL in Scripts
  • Why "Polyglot Programming" or "Do It Yourself Programming Languages" or "Language Oriented Programming" sucks?
  • Groovy Database Resource Handling
  • Containerize Gradle Apps and Deploy to Kubernetes With JKube Kubernetes Gradle Plugin

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: