Converting Java code to Kotlin code

From the menu select Code | Convert Java File to Kotlin File and kaboom! Your task is done. Your first Kotlin activity is ready. As a means of verifying everything is fine, we suggest you run the project once. If you can see Hello World on the emulator or device that means you have successfully configured Kotlin for Android.

Or, create a new Kotlin file (File | New | Kotlin File/Class), and then paste your Java code into that file, when prompted, click Yes to convert the code to Kotlin. You can check Don't show this dialog next time, which makes it easy to dump Java code snippets into your Kotlin files:

Have a watchful eye on such conversion that IDE is doing for you. With great power comes great responsibility. It's always better to check whether IDE has done the right thing for you or not. IDE is not yet that smart and stable that it can convert the code with optimization as well.