How to add Java 9 to Android Studio?

Question

I am using Robolectric library and the latest version of it v4.3.1 requires Java 9 to run. I am trying to point JRE on edit configurations but I am not finding Java 9 in the drop-down even though I have already installed it. It would be really helpful if somebody can please explain!

Please check Java 9 installed.

Answer 1

The only workaround to run Robolectric test in the Android Studio is to change JRE for the test task.

Select IDE menu Run -> Edit Configuration and then change the option from the picture to the location of JDK9:

Answer 2

Tests can run on prior versions as a temporary workaround

You will not be able to run Robolectric against SDK 29 for now (27 April 2020), but this will likely be updated in the future. Currently, as all of the answers before me pointed out, there is no support of Java 9 or later in Android Studio.

But if you are here to make your Robolectic tests run you could simply avoid SDK 29 by setting the Robolectric @Config annotation for your class. Robolectric will simply run your tests against all of the supported SDK versions of your app except 29.

Implement

Set the maxSdk and minSdk versions to run on. This can be based on the app's min and max SDK versions, or set to one version like below in order to make tests faster.

import androidx.test.ext.junit.runners.AndroidJUnit4
import org.robolectric.annotation.Config
import org.junit.runner.RunWith
import android.os.Build

@RunWith(AndroidJUnit4::class)
@Config(maxSdk = Build.VERSION_CODES.P, minSdk = Build.VERSION_CODES.P) // Value of Build.VERSION_CODES.P is 28
class TestClass {
...
}

Of course it is just another "ugly" patch, but it will get you going until you'll be able to run tests against all of the desired SDKs, or at least SDK 29 and all below.

Answer 3

So far Android doesn't support Java 9. As per documentation, Android supports all Java 7 features and a part of Java 8 features.

When developing apps for Android, using Java 8 language features is optional. You can keep your project's source and target compatibility values set to Java 7, but you still need to compile using JDK 8.