You can open the samples inside an IDE using the IntelliJ native importer or Eclipse Buildship.
If you are new to Gradle and wish to follow a more detailed tutorial for building Groovy libraries, we suggest you have an look at the Building Groovy Libraries guide.

This sample shows how a simple Groovy library can be built with Gradle. The library has no dependencies aside from the Groovy runtime and the build has minimal configuration.

build.gradle
plugins {
    id 'groovy'
}

version = '1.0.2'
group = 'org.gradle.sample'

repositories {
    jcenter()
}

dependencies {
    implementation 'org.codehaus.groovy:groovy-all:2.5.7'
}
build.gradle.kts
plugins {
    groovy
}

version = "1.0.2"
group = "org.gradle.sample"

repositories {
    jcenter()
}

dependencies {
    implementation("org.codehaus.groovy:groovy-all:2.5.7")
}

To build the library:

$ ./gradlew jar

BUILD SUCCESSFUL in 6s
2 actionable tasks: 2 executed

For more information, see Groovy Plugin reference chapter. You can also get started quickly using the Build Init Plugin.