When you clone the corda or cordapp-template repos, they will default to the master branch. The master branch is being continuously developed upon, and its features may not align with the state of Corda as described in the docs. Additionally, the master branch of the CorDapp template may break in response to changes in the main corda repo.
When developing on Corda, you should always check out the latest milestone (i.e. stable) branch instead. For example, to check out milestone 0, you'd run ``git checkout release-M0``.
Many users have faced issues when running versions of Java that are either outdated, or are produced by organisations other than Oracle (e.g. OpenJDK). The errors generated by these issues will not always clearly point to the JDK as the cause. If in doubt, check your JDK version by following the instructions `here <https://java.com/en/download/help/version_manual.xml>`_. You can download the latest version of Oracle's JDK `here <http://www.oracle.com/technetwork/java/javase/downloads/index.html>`_.
JavaFX is not bundled with OpenJDK. If you are using OpenJDK and get an 'Unresolved reference: javafx' error, this means that you need to install OpenJFX.
If you have APT installed and OpenJFX is part of your Unix distribution's package list, you can do this by running ``sudo apt install openjfx``, and possibly ``sudo apt install libopenjfx-jav``. Other users will want to refer to the guide `here <https://wiki.openjdk.java.net/display/OpenJFX/Building+OpenJFX>`_, or to the list of Community Builds `here <https://wiki.openjdk.java.net/display/OpenJFX/Community+Builds>`_.
If still have problems, the JetBrains website has more information on `here <https://www.jetbrains.com/help/idea/2016.2/working-with-gradle-projects.html>`_.
If IDEA refuses to open a project because an SDK has not been selected, you may need to fix the project structure. Do this by following `these instructions <https://www.jetbrains.com/help/idea/2016.2/configuring-global-project-and-module-sdks.html>`_. The correct JDK is often found on a path such as ``jdk1.8.0_xx…/Contents/Home``. Ensure that you have the Project language level set at 8.
If you are having trouble selecting the correct JDK, the JetBrains website provides the `following guidelines <https://intellij-support.jetbrains.com/hc/en-us/articles/206544879-Selecting-the-JDK-version-the-IDE-will-run-under>`_.
1. Via the initial project opening screen, by using the ``Configure > Plugins`` tab.
2. From an open IDEA project, by clicking ``IDEA -> Preferences ...`` (on OS X) or ``File -> Settings`` (on Windows). Select the Plugins bar to confirm that Kotlin is installed and up-to-date.
