ma/nextflow/docs/reference/stdlib-groovy.md

(stdlib-groovy)=

Groovy and Java classes

Any Groovy or Java class that is available to Nextflow at runtime can be used in a Nextflow script. The following classes are imported by default:

• groovy.lang.*
• groovy.util.*
• java.io.*
• java.lang.*
• java.math.BigDecimal
• java.math.BigInteger
• java.net.*
• java.util.*

All other classes must be referenced by their fully-qualified name:

def vals = [1, 2, 3]
println groovy.json.JsonOutput.toJson(vals)

:::{note} The set of classes in Nextflow's runtime classpath can change between different Nextflow versions. As a best practice, any code that uses classes outside the Nextflow standard library should either be refactored to only use the Nextflow standard library or be refactored as a {ref}plugin <dev-plugins-page> with explicit dependencies. :::