code for https://medium.com/@dpreussler/speed-up-your-android-gradle-build-baa329cdb836

speedup.gradle

apply plugin: 'checkstyle'
apply plugin: 'pmd'



task checkstyle(type: ParallelCheckstyle) {
    configFile file("${project.rootDir}/config/checkstyle/checkstyle.xml")
    source 'src/main/java'
    include '**/*.java'
    classpath = files()
}

task pmd (type: ParallelPmd) {

    description 'Run pmd'
    group 'verification'
    ignoreFailures true

    ruleSetFiles = files("${project.rootDir}/config/pmd/custom-pmd-ruleset.xml")
//    ruleSets = ["java-basic", "java-strings", "java-design", "java-unusedcode"]
    source = fileTree('src/main/java')

    reports {
        xml.enabled = true
        html.enabled = true
    }
}

@ParallelizableTask
class ParallelCheckstyle extends Checkstyle {
}

@ParallelizableTask
class ParallelPmd extends Pmd {
}