Groovier: Implement interface in Groovy using closure

Groovy’s closure can be used to implement the interfaces with pretty ease. This can come handy when creating scaffolding of code or creating mocks for testing.

Single method interface with same implementation

interface AwesomeInterface {
    void x(String x)
    void y()
}

def interfaceImpl = 
    { String str -> println("Implementation of methods of interface with value: ${str}") } as AwesomeInterface

interfaceImpl.x("Awesome")
interfaceImpl.y() // will call same implementation with null arguments

Output

Implementation of methods of interface with value: Awesome
Implementation of methods of interface with value: null

Multiple methods implementation in an interface

interface AwesomeInterface {
    void x(String x)
    void y()
}
// Use Map as method name as key and Closure as an argument with the implementation 
def interfaceImpl = [
    x: { String str -> println("Implementation method x() of interface with argument: ${str}") },
    y: { println("Implementation of method y() of interface") }
        ] as AwesomeInterface
interfaceImpl.x("Awesome")
interfaceImpl.y() 

Output

Implementation method x() of interface with argument: Awesome
Implementation of method y() of interface