What is Java Development Kit (JDK)?

Java Development Kit (JDK) is a programming platform which allows you to create and develop robust projects in Java Programming Language. It is commonly confused with Java Runtime Environment (JRE) by novice programmers. However, JDK holds the necessary elements to create cross-platform Java applications.   

JDK as a platform makes Java platform independent, robust and portable, making Java extremely popular among developers. According to Statista, Java is used by 30.55% of people worldwide. If you, too, wish to benefit from Java, learning about JDK is a crucial first step. The Java Development Kit is a set of tools and libraries that we use to write Java application programs and run Java applications. Read along to learn more! 

Table of Contents

1) Understanding what is Java Development Kit 

   a) Architecture of JDK   

2) Components of JDK in Java

3) JDK versions   

4) How to download Java Development Kit 

5) Difference between the JDK and JVM

6) Conclusions 

Understanding what is Java Development Kit

The Java Development Kit or JDK is a bundle of necessary tools and libraries which aids you in developing projects using Java Programming Language. Many of you who may have already used  it for educational purposes would be familiar with Java Runtime Environment (JRE). A JRE is part of JDK, which contains the necessary tools like Java Virtual Machine (JVM) and other Java Libraries.    

If you have programmed in Java, you would’ve realised Java Runtime Environment and its libraries are more than capable of running a Java Program. This makes you wonder, “Why do you need JDK in the first place?”. This is where the stark difference between running a program and developing actual projects comes into play.    

Developing projects in Java requires the necessary tools, which are only available in JDK. JDK comes with the standard JRE and, by Extension, JVM, and it also has additional tools and necessary libraries a developer may need. 

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Architecture of JDK 

Java’s JDK consists of JRE, and thus all standard tools available in JRE. This normally includes the JVM, a Compiler, an Interpreter and other tools. Let's understand the function of each of these components in Java architecture.  

1) Java Runtime Environment: Java Runtime Environment is a subset of JDK. JRE is available for download and installation separately. This is for people who wish to program in Java but do not wish to approach developing projects.Standalone JRE is crucial because it lets people get familiar with the programming language before committing to it. Java Runtime Environment is relatively lightweight and occupies less space than JDK.    

2) Compiler: JDK comes with a default compiler known as Javac. Java has many compilers depending on its runtime and environment. Some common examples of its Compilers are Javac, Eclipse Compiler for Java (ECJ) and GNU Compiler for Java (GCJ), but you’ll find JDK integrated with Javac. This compiler is responsible for converting a Java program into a bytecode. 

3) Java Virtual Machine: Java Virtual Machine serves as an engine for Java Programming Language. It takes a file after it's turned into a byte code. The nature of the byte code and JVM depends upon the Operating System (OS). JVM acts as an intermediator and platform between your OS and program. This makes your Java program extremely versatile and platform-independent as a result. This means you can port your program into another system, and it will run fine if a JDK is installed.

4) Just In Time Interpreter: Java has Just in Time Interpreter, which converts the byte code into machine code that your system can process. This process makes Java one of the few languages to be compiled and interpreted.

5) Additional components in JDK: Some other components necessary for Java project creation are java, javac, javadoc, jar, jps, jmc, jhat, javaws, javah, Jconsole, idlj and javap. Each component has its respective functions, such as generating documents for comments and jar file management.   

 They are the driving force behind the working mechanism of JRE. Some of these components even are necessary for debugging and an applet without the need for the internet. 



 

Components of JDK 

The JDK  comprises of various components that are vital to its functioning. Here are their descriptions shown below:

Java

The Java component is basically a loader that is designed to work across all Java applications. The Java tool does the job of interpreting the class file that is generated by ‘javac’. The single java launcher is utilised for the developing and deploying the software application. The JRE which was used to launch the deployment is no longer necessary for this task, and it also does not exist with the Sun JDK because of being replaced by the new Java loader. 

Java Runtime Environment (JRE)

The JRE is a software application that is designed to execute Java programs in the appropriate manner as they are programmed to be. The JRE is essentially the backbone and foundational technology that is meant to communicate as an intermediary between the Java program and the Operating System (OS). 

It plays the role of a translator and facilitator, thereby providing the necessary resources for helping Java software execute on any OS without any extra modifications. More importantly, developers must note that any software program usually requires a runtime environment that offers easy access to memory and other important resources like program files and system dependencies. 

javadoc

The javadoc component of the JDK generates the necessary documentation for any comments that are added in the source code. The command basically does the job of parsing the declarations and comments from the documentation into a collection of Java source files and produces a set of HTML pages that accurately describe both the public and protected classes, constructors, interfaces, nested classes, fields and methods. 

Created by Sun Microsystems for the Java language for generating API documentation in the HTML format from the Java source code. The HTML format is utilised to make the process of hyperlinking related documents easier. 

Applet viewer

The Applet viewer is a command-line program designed to run applets in Java. It is offered to the developers with the SDK and helps them test their Java applets before they can run it in any browser. The Applet is a special kind of software application included within the HTML page and can be stored by users in a web page and executed inside a web browser. 

Further, the Applet’s code then gets transferred to the system and then the code is executed by the JVM in the browser followed by a display of the output. Users must take note that the browser basically needs to be Java enabled to run the applet. They also need to define a class that inherits the applet for a smooth creation of the applet. 

JConsole

JConsole is a Graphical User Interface (GUI) monitoring tool that is built to comply with the Java Management Extensions (JMX) specification. The tool basically utilises the extensively developed instrumentation of the JVM in order to provide developers with the necessary information pertaining to the performance and resource consumption of software applications that are running on the Java platform. 

The ‘JDK_HOME/bin’ contains the jconsole executable. This directory contains the installation of the JDK. Now if the directory is in the user’s system path, they can start JConsole by typing in the ‘jconsole’ command in the system’s shell prompt. The alternative is to type the complete path to the file that needs to be executed.

javap

The ‘javap’ command can be used if a user wants to disassemble one or multiple class files. The syntax is ‘javap [options] classes...’, wherein ‘options’ specifies the options available to the user in the command-line. ‘Classes’ basically specified the classes that are separated by spaces to be further processed for annotations.

JDK versions  

Before downloading and installing Java, decide which version of JDK you wish to install. You can find many versions of JDK and JRE on its website. Oracle has two core types of JDK, a standard edition and an open-source edition. For new programmers, the standard version might allow you to test your capabilities and build experience before venturing further into the programming world.    

Java also categorised its JDK based on OS, with each version available for download. It can be downloaded for Windows, Linux and MacOS-based files. Additionally, its programs are very portable, so if you wish to change your system later, your code can still work on a different OS.   

JDK also has a category based on your system's processing power and capabilities. Java’s JDK files come in 32- and 64-bit editions for all OS, including Ubuntu, ARM Linux, and Windows-based JDK files. You can run 32-bit JDK on a 64-bit system. However, you are not required to do so, as it serves no purpose.    

Lastly, you need to decide on the correct version of Java. Generally, most users choose the latest version of its runtime environment. You can also consider which Java version has Lifetime Support (LTS) from Oracle. You do not need to worry too much about the Java version as its latest version supports the codes written in its oldest version and vice versa. 

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How to download Java Development Kit  

Downloading and installing JDK might seem complicated, but with some guidance, it won’t be tough. Follow these steps to download JDK and install it on your system successfully: 

Step 1: Click on this link to guide you to Oracle’s Java download page.    

Step 2: Select the Java version in you wish to install. Currently, its latest versions are Java 20 and Java 17 LTS.  

Step 3: Once you have downloaded the JDK from Java Downloads, Start the JDK installer. You can click twice on the file name or the installer’s icon. 

Step 4: Check for the location of the JDK software’s installation and remove the downloaded file to recover space.  

Additional Tip: JDK installer cannot install when another version of it already exists on a system. This rule does not apply to all JDK systems but applies to most of them. As a result, the JDK installer will likely uninstall your previous version of JDK during the installation process. 

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Difference between the JDK and JVM

The JDK and JVM are both foundational concepts of the Java language. Although these are not utilised in programming, it is vital for developers to be well-versed with their basics and usage. Now there is a utility named ‘java’ inside the bin directory of the JDK, which is designed to take a Java application encompassing a runnable main method. This method is then executed as a software application program. 

When the source code of any Java application is put for compilation, it is converted into bytecode. This converted code acts as an intermediary between the Java source code and the low-level machine code. Further, upon invocation of the Java utility, a Java Virtual Machine is then created. This VM utilises a Just-in-Time (JIT) compiler to convert the bytecode into machine code. Such an on-the-fly conversion from the bytecode to low-level computer instructions is vital to the cross-platform and hardware-agnostic nature of the Java application. 

Below are the various differences between JDK and JVM:
 

Conclusion

Java Development Kit is an essential component of programming in Java. Hopefully, this blog helped you understand what JDK is, how it works, and its components. You’ll be more informed on how to download JDK and which version is the correct choice for you. Thank you for reading. 

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