Unable to instantiate application - java.lang.ClassNotFoundException: Didn't find class "com.xxxxx.App" on path: /data/app/com.xxxxx-1.apk

This is the error everytime I run the app:

    E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to instantiate application com.xxxxx.App: java.lang.ClassNotFoundException: Didn't find class "com.xxxxx.App" on path: /data/app/com.xxxxx-1.apk
    at android.app.LoadedApk.makeApplication(LoadedApk.java:509)
    at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4657)
    at android.app.ActivityThread.access$1400(ActivityThread.java:159)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1376)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:176)
    at android.app.ActivityThread.main(ActivityThread.java:5419)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:525)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassNotFoundException: Didn't find class "com.xxxxx.App" on path: /data/app/com.xxxxx-1.apk
    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:64)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
    at android.app.Instrumentation.newApplication(Instrumentation.java:992)
    at android.app.LoadedApk.makeApplication(LoadedApk.java:504)
    at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4657) 
    at android.app.ActivityThread.access$1400(ActivityThread.java:159) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1376) 
    at android.os.Handler.dispatchMessage(Handler.java:99) 
    at android.os.Looper.loop(Looper.java:176) 
    at android.app.ActivityThread.main(ActivityThread.java:5419) 
    at java.lang.reflect.Method.invokeNative(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:525) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862) 
    at dalvik.system.NativeStart.main(Native Method)

Here some info:

JavaVersion.VERSION_1_8        (I cannot use 1.7 because of a library)
buildToolsVersion '24.0.0'
compileSdkVersion & target 24  (also tried 23)
gradle 2.2.0-alpha4            (also tried with 2.1.0)

I have instant run disabled.

I have a class named App that extends Application, so in AndroidManifest.xml I have <application android:name="com.xxxxx.App"

Please don't mark this question as duplicate, because I have already tried all the solutions given, but I cannot get rid of this error.

I was having the same error and just cleaning the project solve it for me. it seems a bug in the new version of android studio.

Have you tried running the app on another device/emulator?
I experienced this problem once because I was the 2nd user on the device that I was trying to run it on. If that's the case, you will have to switch to the primary user(owner) every time you wish to run your app.

remove the app from your mobile phone then build => clean project and try installing again