This page provides some support for the readers of A Natural Introduction to Computer Programming with Java.
You need to download and install the Java SE Development Kit (JDK) to compile and run Java programs. You can find information related to the installation and compilation if you check the comments at the beginning of file Game.java.
Here is some information related to downloading free program editors.
There are many tools that can be used to edit and compile Java programs. NetBeans is an IDE (Integrated Development Environment) that has even been programmed with Java.
All the source programs presented in the book are available through the links in the book page.
IC8, the simulator program for the imaginary computer discussed in Chapter 4 of the book, can be used through the icon on the main page.