Computational Problem Solving with Java and Interactive Object Graphics

As we discussed in Section 1.6, to develop Java programs, you must install or have available the Java Development Kit (JDK). Only the JDK includes necessary tools, including the Java compiler (javac).

JDK installers are specific to the operating system of your computer. As we’ve described, the JVM executes Java bytecode in a platform-independent manner. That is possible because there is a different JVM for each platform which runs Java bytecode by translating bytecode to native platform instructions.

To download an installer, visit Adoptium¹ with a browser from the computer you plan to use for Java development. You will be offered the option to download a matching installer for OpenJDK, an open-source implementation of the Java Platform, Standard Edition. Download and run the installer. Follow the instructions for your particular operating system to install the JDK.

JDK tools like javac are executed using programs like a terminal or command prompt program. Every operating system provides one or more terminal programs with a shell for executing commands, and they differ in subtle ways. Typically, these programs start as black boxes that accept text commands and usually output results as text as well. Terminal programs may run a shell, which provides more sophisticated capabilities for running commands and interacting with the underlying operating system. The shell you choose also can impact the commands you may use. While we cannot cover the details of every terminal and every shell, we will point out common pitfalls for popular options.

One pitfall often experienced after a new installation is the inability to access JDK commands from the shell. For example, assume the JDK installs successfully, the new user opens and terminal running a shell, and proceeds to test the new installation by entering the command java -version, which should print the version of Java that is installed. Instead, the command is not found and an error is printed. Frustrating!

If the JDK is indeed installed successfully, the program is almost always automatically associated with the directory paths that a shell searches to find an entered command program. Only if the command program can be found at one of those predetermined paths will the command be executed. These search paths are stored in an operating system environment variable, frequently named PATH. For example, on Windows you can search for and start the "Environment Variables" configuration program to inspect the PATH environment variable value and edit it to add a file system path to the bin subdirectory under the location of where the JDK is installed. It is the bin subdirectory where you’ll find the JDK commands. If your systemm cannot find the java command after entering into a shell, check your environments search location paths.

A Java source code program is a "plain text file." When a file is referred to as "plain text" the implication is that the file contains characters only, from the default character set of the file. You will find no formatting or other commands that set font family or font style, such as bold or italics. Character codes are the only data in the file. One important feature of a programming editor is that it edits and saves plain text files.

Another important feature of a good programming editor is knowledge of the programming language being edited. This gives the editor the ability to categorize and colorize the symbols and keywords in a given program file, and to format and indent the program’s text automatically, using standard rules. Modern editors can do even more, such as detecting syntax errors or performing advanced context aware searching and editing of the file.

There are many good programming editors available for use. You may choose any editor known to be suitable for writing Java programs. If you do not have an editor installed or one that is preferred, the Visual Studio Code² (VSCode) editor from Microsoft, is a good option. Note that the VS Code editor is different that the Visual Studio Integrated Development Environment (IDE), which is a much more full-featured environment. VSCode is a simple and freely available editor suitable for many programming languages. Visit the url https://code.visualstudio.com, download a suitable installer, and install it on your computer. Using a suitable editor will pay off quickly.

If you do choose to install VSCode, consider adding the Extension Pack for Java³. Installing this extension pack will add functionality to the editor specific for the Java programming language.