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Computational Problem Solving with Java and Interactive Object Graphics

Mark F. Russo, PhD

Section 1.6 The Java Development Kit

The Java Development Kit (JDK) is a software development kit that allows developers to create, compile, and run Java applications. It includes tools, libraries, and documentation necessary for Java development. The JDK is available for multiple platforms, including Windows, macOS, and Linux.
The key components and features of the Java Development Kit include the following.
  1. Java Compiler (javac) for compiling source code into bytecode.
  2. Java Virtual Machine (JVM) which is responsible for executing Java bytecode.
  3. Java Runtime Environment (JRE) which contains the JVM and essential class libraries required to run Java applications.
  4. The Java Shell (JShell) is a Read-Evaluate-Print Loop (REPL) application that runs in a terminal. It evaluates entered declarations, statements, and expressions immediately and prints results.
  5. Other Java Development Tools including the Java Debugger (jdb) and the Java Archive (JAR) tool.
  6. Libraries and APIs, a large set of core class libraries and APIs that provide pre-built functionality for various tasks.
  7. Development Documentation, a comprehensive set of documentation that describes all of the above.
One item worth highlighting is the platform-independence of the Java Virtual Machine (see Figure 1.6.1). The JVM plays a fundamental role in achieving Java’s "write once, run anywhere" capability. Since the JVM executes bytecode, which is a platform-neutral format, Java programs can be executed on any system that has a compatible platform-specific JVM. This makes Java programs highly portable and eliminates the need to recompile the code for different operating systems or architectures.
Figure 1.6.1. Java programs are platform-independent. The JVM is not.
Another item worth expanding upon is the JShell REPL. JShell provides a lightweight and interactive way to explore and experiment with Java code. It is particularly useful for learning the Java language, prototyping, and debugging small code snippets. It offers a flexible and dynamic environment for interactive Java development without the need to set up a complete project structure or compile and run separate Java files. JShell tracks history and stores past results. It also acts as an interactive help tool.
In verbose mode JShell not only produces the output from evaluating Java, but it also prints the type of the result -- something that we will be using extensively in the next chapter.
Overall, the Java Development Kit is an essential tool for Java developers, providing everything needed to create, compile, and run Java applications. It offers a rich set of development tools, libraries, and documentation, enabling developers to build robust and platform-independent Java software.
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