Groovy compiler does not accept java 8 Lambdas

Question

As , we know , Groovy syntax accepts closures . Today also, Java 8 adds in its syntax closure .

However , When i write java8 closure in groovy file , i get an error like the following :

Person.findAll().stream().filter(e-> e.age > 20)

We get this error :

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Script1.groovy: 7: unexpected token: -> @ line 7, column 39.
   Person.findAll().stream().filter(e-> e.controllerId > 0)
                                         ^

1 error

Nevertheless , the following works successully :

Person.findAll().stream()  

Solution

Yeah, the Groovy parser does not accept Java 8 Lambdas (not closures).

You can use a closure in place of it (assuming you're on Groovy 2.3.*)

ie:

Person.findAll().stream().filter( { e -> e.age > 20 } )

edit:

Groovy 3.0+ will accept lambda format

Comments

[Will]

Groovy is scheduled to accept Java's 8 syntax on version 3

[Abdennour TOUMI]

Really , java 8 will let all programmer to not return to groovy

[tim_yates]

@AbdennourToumi Apart for the ease of scripting, meta-programming, dynamic types, AST transformations, data parsing, ease of DSL creation, and being able to Grab resources, you may be right ;-)

[Daniil Shevelev]

I tried following code in Groovy and "x" is the array and not an element. "Arrays.stream(array).filter({ x -> x.equals(dependent) || x.equals(governor) }).toArray();" Any suggestions?

[tim_yates]

@DaSh my guess is that what you have named array is a list

[medge]

@tim_yates using @CompileStatic in this case generates compilation errors "filter in java.util.Stream cannot be applied to groovy.lang.Closure". IntelliJ's proposed fix was something on the order of lst.stream().filter({ from, to -> to.equals(node) } as Predicate<? super Tuple>). This is as of Groovy 2.4.5. Thoughts? (For reference, the lst var was a Set<Tuple>)

[Gangnus]

@tim_yates Please, add a variant for two arguments lambdas, for in Java it needs braces, and in Groovy we need to omit them. And thank you, it helped anyway.

[James]

@AbdennourTOUMI it's 2021 w/ Java 16 fairly well established in the wild and I still very much prefer Groovy over Java ¯_(ツ)_/¯