Add another java source directory to gradle script

I have a slightly different approach with a Gradle 4.6:

sourceSets {
    main {
        java {
            srcDir 'src/main/java'
            srcDir 'build/swagger-code-dummy/src/main/java'
        }
    }
}

as you can see, I had to specify the directories with the "/main/java" subdirectories as well, otherwise gradle/intellij was not setting the right path.

Maybe this helps someone else too :)

The question is about "Adding"; the question of the text is describing a more concrete scenario. If one just wants to add an existing directory, this is the way to add:

sourceSets.main.java.srcDirs += ['src/gen/java']

An example full build.gradle is as follows:

apply plugin: 'java'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'com.squareup:javapoet:1.12.1'
}

sourceSets.main.java.srcDirs += ['src/gen/java']

JavaPoet s a Java API for generating .java source files. It is just used as example library for the build.gradle file.

I agree with @JB Nizet about respecting standard conventions. If you still insist on being an Anarchist though:

You already have src declared in your sourceset, why not add src1 and src2 as well? You can add them to the same sourceset, or define a sourceset per module if you want.

sourceSets {
    main {
        java {
            srcDirs 'src'
            srcDirs 'src1'
            srcDirs 'src2'
        }
    }
 }

To reference files outside the project, see this answer.