Android Studio 3.0 Execution failed for task: unable to merge dex

Question

android studio was getting build error while build execution with following:

Error:Execution failed for task \':app:transformDexArchiveWithExternalLi

Answer 1

For me, the problem was the use of Java 1.8 in a module, but not in the app module. I added this to the app build gradle and worked:

android{
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }