Learning Groovy 3: Java-Based Dynamic Scripting

© Adam L. Davis 2019

Adam L. DavisLearning Groovy 3https://doi.org/10.1007/978-1-4842-5058-7_8

8. Traits

Adam L. Davis¹ 

(1)

New York, NY, USA

 

Traits are like interfaces with default implementations and state.

Those familiar with Java 8 know that it added the default methods feature to interfaces. Traits are similar to Java 8 interfaces but with the added ability to have state (fields). This allows more flexibility but should be treated with caution.

Defining Traits

A Trait is defined using the trait keyword:

1   trait Animal {

2       int hunger = 100

3       def  eat() { println "eating"; hunger -= 1 }

4       abstract int getNumberOfLegs()

5   }

As this code demonstrates, Traits can have properties, methods, and abstract methods. If a class implements a ...