Product variants

BaseConfiguration.java

public class BaseConfiguration {
    public static final String API_URL = "https://someapi.wolox.com.ar";
}

build.gradle

buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

build2.gradle

signingConfigs {
        stage {
            storeFile file('keystore/stage.keystore')
            storePassword 'android'
            keyAlias 'androidandroiddebugkeyDebug'
            keyPassword 'android'
        }
        production {
            storeFile file('keystore/playstore.keystore')
            storePassword store_password
            keyAlias key_alias
            keyPassword key_password
        }
    }

build3.gradle

apply from: 'keystore.gradle'

build4.gradle

productFlavors {
        stage {
            signingConfig signingConfigs.stage
            applicationId defaultConfig.applicationId + ".stage"
            versionName defaultConfig.versionName + "-stage"
        }

        production {
            signingConfig signingConfigs.production
        }
    }

Configuration.java

public class Configuration extends BaseConfiguration {
    public static final int ITEMS_PER_PAGE = 5;
}

keystore.gradle

ext.key_alias='playstore'
ext.key_password='playstore'
ext.store_password='playstore'