How to lock the screen of an Android device on Android 4.4 and 5.0+

Question

I want to lock the device screen. I found a solution on the Internet and I am using this tutorial http://rdcworld-android.blogspot.in/2012/03/lock-phone-screen-programmtically.html . Unfortunately, after testing, it does not work for Android 4.4 and 5.0+. It works fine on Android 2.2+. So, how to lock the screen of the device for Android 4.4 and 5.0+, and not reduce the brightness.