=============================
Using Kotlin in IntelliJ IDEA
=============================

Working with Kotlin from within IntelliJ IDEA is relatively straightforward.
Remember that you can `get the full professional version`_ of this IDE to use
for free on your own PC, but you will need to `apply for a student license`_.

When you run IntelliJ, choose the option to create a new project, then make
sure you've selected 'Kotlin/JVM' as the project type.

.. figure:: newproj.png
   :scale: 75 %
   :align: center

   First page of IntelliJ project creation wizard


The Kotlin REPL
===============

#. To run the REPL, choose :menuselection:`Tools --> Kotlin --> Kotlin REPL`
   from the menu bar.  This will open a new panel at the bottom of the IDE
   window, within which the REPL is running.

   Try entering a line of Kotlin code. Press :kbd:`Ctrl+Enter` to execute it.

   .. figure:: repl.png
      :scale: 75 %
      :align: center

      Kotlin REPL running within IntelliJ

#. Now try some code that spans multiple lines:

   .. code-block:: kotlin

      var sum = 0
      for (n in 1..10) {
        sum += n
      }

   You can run this loop by pressing :kbd:`Ctrl+Enter` after having entered
   the code for the loop body.  To see the result, enter ``sum`` and press
   :kbd:`Ctrl+Enter` again.

.. note::

   One limitation of the REPL in IntelliJ is that repeated invocations of
   ``println()`` within the same block of code won't produce output on
   separate lines!


Creating & Running Programs
===========================

#. Right-click on the :file:`src` folder in the *Project* panel on the left
   of the IDE and choose :menuselection:`New --> Kotlin File/Class`.  Enter
   ``hello`` as the name, leave the *Kind* field set to 'File' and click
   :guilabel:`OK`.

#. In the resulting file :file:`hello.kt`, implement a simple program:

   .. code-block:: kotlin

      fun main(args: Array<String>) {
        println("Hello World!")
      }

#. To run this program, choose :menuselection:`Run --> Run...` from the menu
   bar, or press :kbd:`Alt+Shift+F10`.  In the resulting pop-up menu, click
   on the 'HelloKt' option.  The program will compile and run, and output
   will appear in the *Run* panel at the bottom of the IDE.

   Note that this will create a run configuration of the program.  You can
   run it subsequently by clicking on the 'green triangle' in the toolbar at
   the top right, or by choosing :menuselection:`Run --> Run 'HelloKt'`,
   or by pressing :kbd:`Shift+F10`.

#. Another thing you can do in IntelliJ is view the JVM bytecode generated
   for a particular Kotlin file.  Try this now by opening :file:`hello.kt`
   and choosing :menuselection:`Tools --> Kotlin --> Show Kotlin Bytecode`.


.. _get the full professional version:
   https://www.jetbrains.com/idea/download/

.. _apply for a student license:
   https://www.jetbrains.com/shop/eform/students