so according to GitHub the project is:
Java 60.0%
Kotlin 39.6%
We have Retrolambda, Kotlin and all the fun stuff. Changing one line in a Kotlin results in the following build time:
Total time: 23.17 secs
Task timings over 50ms:
143ms blsAndroidmergeDevMultidexLollipopDebugResources
9962ms blsAndroidcompileDevMultidexLollipopDebugKotlin
5330ms blsAndroidcompileDevMultidexLollipopDebugJavaWithJavac
83ms blsAndroidgenerateDevMultidexLollipopDebugJrebelLayout
461ms blsAndroidtransformClassesAndResourcesWithExtractJarsForDevMultidexLollipopDebug
474ms blsAndroidtransformClassesWithRetrolambdaForDevMultidexLollipopDebug
2331ms blsAndroidtransformClassesWithDexForDevMultidexLollipopDebug
426ms blsAndroidtransformResourcesWithMergeJavaResForDevMultidexLollipopDebug
1641ms blsAndroidpackageDevMultidexLollipopDebug
113ms blsAndroidzipalignDevMultidexLollipopDebug