I'm finding the same issue and tried with solution specified but still i'm getting the same error as below
java.lang.NoClassDefFoundError: Failed resolution of: Lokhttp3/OkHttpClient$Builder;
Caused by: java.lang.ClassNotFoundException: Didn't find class "okhttp3.OkHttpClient$Builder" on path: DexPathList[[zip file "path" ]]
my gradle's is like
compile 'io.realm:android-adapters:1.4.0'
compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
compile 'io.reactivex:rxandroid:1.1.0'
compile 'io.reactivex:rxjava:1.1.3'
compile 'com.squareup.retrofit2:retrofit:2.3.0'
compile 'com.squareup.retrofit2:converter-gson:2.3.0'
compile 'com.squareup.retrofit2:adapter-rxjava:2.3.0'
compile 'com.squareup.okhttp3:okhttp:3.9.0'
I have my application classes which extends MultidexApplication.