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build – Android gradle buildTypes: Duplicate class

Posted by: admin April 23, 2020 Leave a comment


I’m converting my app to use gradle, and I’m trying to use the buildTypes. I have a Constants class which I wish to modify for my release build. So I have a file at src/main/java/my/package/name/Constants.java and at src/release/java/my/package/name/Constants.java.

When I try to build this, gradle tells me the build failed on the Constants file in my release buildtype, with the error that it’s a duplicate class.

I also tried adding a different sourceSet for this in my build.gradle like this:

sourceSets {
    main {
        java.srcDirs = ['src/main/java'];
    release {
        java.srcDirs = ['src/release/java'];

But this still gives me the same error. So I’m wondering, what am I doing wrong here?

How to&Answers:

You can not have a class in main and release. You need to split it into something like debug and release.

gradle will merge the source sets for each buildType with main.
This is the reason, why the class gets duplicated in your release build.

So the rule is: put a class into main, or in every buildType but not both.


The answer from “fix” helped me on the way, but I got an error from the main Gradle, saying a constant was missing (in my class Config). This since I had my class only in paid and free version and not in main. Could not find the Config class.
Im not sure if this is a bug in Studio… I finally solved it with the following:

buildTypes {

    release {
        buildConfig "public static final boolean XYZ = false;"


And the instead of using my Config.XYZ class constant I used buildConfig.XYZ