Freeline it's an open source solution to speed up your compiling, like 2 seconds compared to 2 minutes in the old way. It's super fast because of the increment build only for the changed class.

1. Github: https://github.com/alibaba/freeline
2. QCon Shanghai 2016 Presentation: https://github.com/pjq/QConShanghai2016/tree/master/Mobile

1. Add to the build.gradle in the root director of your project

 buildscript {
     dependencies {
         classpath 'com.android.tools.build:gradle:2.2.2'
         classpath 'com.google.gms:google-services:1.4.0-beta3'
 
         //Freeline
         classpath 'com.antfortune.freeline:gradle:0.8.2'
     }

2. Add to the app/build.gradle

//Freeline
apply plugin: 'com.antfortune.freeline'

android {
     ...
     freeline {
         hack true
         productFlavor 'flavorA'
     }
 
     productFlavors {
        flavorA {}
     }
     ...
}