@ParametersAreNonnullByDefault for all subpackages includes src, test and androidTest

app build.gradle

apply plugin: 'com.android.application'
apply from: 'nonnull.gradle'

android {
    compileSdkVersion 24
    buildToolsVersion "24.0.2"

    [...]
}

checkstyle.xml

<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
          "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
          "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
<module name="Checker">
  [...]
  <module name="JavadocPackage"/>
  [...]
</module>

  

nonnull.gradle

/**
  *  File: nonnull.gradle
  *
  *  Generates package-info.java for appropriate packages
  *  inside main src, test and androidTest folders.
  *
 */
task generateNonNullJavaFiles(dependsOn: "assembleDebug", type: Copy) {
    group = "Copying"
    description = "Generate package-info.java classes"

    def mainSrcPhrase = "src" + File.separatorChar + "main" + File.separatorChar +
            "java" + File.separatorChar
    def mainTestSrcPhrase = "src" + File.separatorChar + "test" + File.separatorChar +
            "java" + File.separatorChar
    def mainAndroidTestSrcPhrase = "src" + File.separatorChar + "androidTest" + File.separatorChar +
            "java" + File.separatorChar

    def sourceDir = file( "${projectDir}" + File.separatorChar + "src" + File.separatorChar +
            "main" + File.separatorChar + "java" + File.separatorChar +
            "com" + File.separatorChar + "company" + File.separatorChar + "packagename" )
    def testSourceDir = file( "${projectDir}" + File.separatorChar + "src" + File.separatorChar +
            "test" + File.separatorChar + "java" + File.separatorChar +
            "com" + File.separatorChar + "company" + File.separatorChar + "packagename" )
    def androidTestSourceDir = file( "${projectDir}" + File.separatorChar + "src" + File
            .separatorChar +
            "androidTest" + File.separatorChar + "java" + File.separatorChar +
            "com" + File.separatorChar + "company" + File.separatorChar + "packagename" )

    generateInfoFiles(sourceDir, mainSrcPhrase);
    sourceDir.eachDirRecurse { dir ->
        generateInfoFiles(dir, mainSrcPhrase)
    }
    if (file(testSourceDir).exists()) {
        generateInfoFiles(testSourceDir, mainTestSrcPhrase);
        testSourceDir.eachDirRecurse { dir ->
            generateInfoFiles(dir, mainTestSrcPhrase)
        }
    }
    if (file(androidTestSourceDir).exists()) {
        generateInfoFiles(androidTestSourceDir, mainAndroidTestSrcPhrase);
        androidTestSourceDir.eachDirRecurse { dir ->
            generateInfoFiles(dir, mainAndroidTestSrcPhrase)
        }
    }
    println "[SUCCESS] NonNull generator: package-info.java files checked"
}

private void generateInfoFiles(File dir, String mainSrcPhrase) {
    def infoFileContentHeader = getFileContentHeader();
    def infoFileContentFooter = getFileContentFooter();
    def infoFilePath = dir.getAbsolutePath() + File.separatorChar + "package-info.java"

    //file(infoFilePath).delete(); //do not use in production code
    if (!file(infoFilePath).exists()) {
        def infoFileContentPackage = getFileContentPackage(dir.getAbsolutePath(), mainSrcPhrase);
        new File(infoFilePath).write(infoFileContentHeader +
                infoFileContentPackage + infoFileContentFooter)
        println "[dir] " + infoFilePath + "  created";
    }
}

def getFileContentPackage(String path, String mainSrcPhrase) {
    def mainSrcPhraseIndex = path.indexOf(mainSrcPhrase)
    def output = path.substring(mainSrcPhraseIndex)

    // Win hotfix
    if (System.properties['os.name'].toLowerCase().contains('windows')) {
        output = output.replace("\\", "/")
        mainSrcPhrase = mainSrcPhrase.replace("\\", "/")
    }

    return "package " + output.replaceAll(mainSrcPhrase, "").replaceAll(
                "/", ".") + ";\n"
}

def getFileContentHeader() {
    return  "/**\n" +
            " *\n" +
            " * Make all method parameters @NonNull by default.\n" +
            " *\n" +
            " * We assume that all method parameters and return types are NON-NULL by default.\n" +
            " *\n" +
            " * e.g.\n" +
            " *\n" +
            " * String trimExampleMethod(String value) {\n" +
            " *     return value.trim();\n" +
            " * }\n" +
            " *\n" +
            " * is equal to:\n" +
            " *\n" +
            " * @NonNull\n" +
            " * String trimExampleMethod(@NonNull String value) {\n" +
            " *     return value.trim();\n" +
            " * }\n" +
            " *\n" +
            " * reverse this behaviour with: @Nullable annotation.\n" +
            " *\n" +
            " */\n" +
            "@ParametersAreNonnullByDefault\n" +
            "@ReturnValuesAreNonnullByDefault\n"
}

def getFileContentFooter() {
    return  "\n" +
            "import javax.annotation.ParametersAreNonnullByDefault;\n" +
            "\n" +
            "import edu.umd.cs.findbugs.annotations.ReturnValuesAreNonnullByDefault;"
}