How to use custom gradle generated constant in android java code

It is really easy to define gradle-generated constants and use those constants in android java code.
For example, I want to use a build type dependent constant RETRY_COUNT.

Gradle's class BuildType has a method:
    public void buildConfigField(String type, String name, String value)

This method can be used like this:

android {
...

    buildTypes {
        release {
            buildConfigField "int", "RETRY_COUNT", "3"
...
        }

        debug {
            buildConfigField "int", "RETRY_COUNT", "10"
...
        }
    }
}

Next, I rebuild my project, open BuildConfig and see:

public final class BuildConfig {
...
public static final boolean RETRY_COUNT = 10;
}