What is the JDK? Introduction to the Java Development Kit

Credits : Javaworld



The Java Development Kit (JDK) is one of three core technology packages used in Java programming, along with the JVM (Java Virtual Machine) and the JRE (Java Runtime Environment). It’s important to differentiate between these three technologies, as well as understanding how they’re connected:

  • The JVM is the Java platform component that executes programs.
  • The JRE is the on-disk part of Java that creates the JVM.
  • The JDK allows developers to create Java programs that can be executed and run by the JVM and JRE.

Developers new to Java often confuse the Java Development Kit and the Java Runtime Environment. The distinction is that the JDK is a package of tools for developing Java-based software, whereas the JRE is a package of tools for running Java code.

The JRE can be used as a standalone component to simply run Java programs, but it’s also part of the JDK. The JDK requires a JRE because running Java programs is part of developing them.

Figure 1 shows how the JDK fits into the Java application development lifecycle.

jw whatisjdk fig1Matthew Tyson
Figure 1. High-level view of the JDK

Just as we did with my recent introduction to the Java Virtual Machine, let’s consider the technical and everyday definitions of the JDK:

  • Technical definition: The JDK is an implementation of the Java platform specification, including compiler and class libraries.
  • Everyday definition: The JDK is a software package you download in order to create Java-based applications.

Get started with the JDK

Getting Java setup in your development environment is as easy as downloading a JDK and adding it to your classpath. When you download your JDK, you will need to select the version of Java you want to use. Java 8 is the version most commonly in use, but as of this writing Java 10 is the newest release. Java maintains backward compatibility, so we’ll just download the latest release.

JDK packages

In addition to choosing your Java version, you will also need to select a Java package. Packages are Java Development Kits that are targeted for different types of development. The available packages are Java Enterprise Edition (Java EE), Java Standard Edition (Java SE), and Java Mobile Edition (Java ME).

Novice developers are sometimes unsure which package is correct for their project. Generally, each JDK version contains Java SE. If you download Java EE or Java ME, you will get the standard edition with it. For example, Jave EE is the standard platform with additional tools useful for enterprise application development such as Enterprise JavaBeans or support for Object Relational Mapping.

It’s also not hard to switch to a different JDK in the future if you find you need to. Don’t worry too much about choosing the correct Java version and JDK package when you are just starting out.

Downloading the JDK

We’ll stick with Java SE for this tutorial, so that we can focus on the core JDK classes and technologies. To download the Java SE JDK, visit Oracle’s official download page. You’ll see the various JDK packages available, as shown in Figure 2.

Before you select the Java SE download, take a minute to look at the other options. There’s a lot cooking in the Java kitchen!

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