What Is JDK (Java Development Kit)?

The Java Development Kit (JDK) is a software package that lets you write, compile, debug, and run Java applications. It bundles the Java compiler (javac), the Java Runtime Environment (JRE), the JVM, and tools like jar, javadoc, and jshell. If you want to build Java software, you need a JDK. If you only want to run Java software, a runtime is enough.

That is the short version. Below, we go deeper: what is inside the JDK, how it differs from JRE and JVM, which version to pick today, and the part most articles skip, the real cost. Yes, JDK is mostly free, but there is one licensing trap that has cost some companies hundreds of thousands of dollars.

What Is JDK in Simple Words

Think of Java as a language, and the JDK as the full workshop you need to build things with that language. The workshop has a compiler that turns your code into something a machine can run, a runtime that actually runs it, and a bunch of small tools for packaging, testing, and fixing problems.

Without a JDK you can still run a Java program someone else built. But you cannot compile your own.

Who needs the JDK?

• Developers writing Java, Kotlin, Scala, or Groovy code on the JVM
• Build servers running Maven, Gradle, or CI/CD pipelines
• Students learning Java for the first time
• DevOps teams who need profiling and diagnostic tools in production

Who does not need the full JDK?

• End users who only run a desktop Java app (the app usually ships its own runtime)
• Production containers that use a trimmed runtime built with jlink

JDK vs JRE vs JVM

A lot of beginners gets confused by these three terms, so here is the cleanest way to see it. They are nested, like Russian dolls.

Term	Full name	What it does	Contains compiler?	Who needs it
JVM	Java Virtual Machine	Executes Java bytecode on your OS	No	Everyone running Java
JRE	Java Runtime Environment	JVM plus core libraries (classes) to run apps	No	Users running Java apps
JDK	Java Development Kit	JRE plus compiler and developer tools	Yes	Developers building Java apps

One-line memory trick: JDK contains JRE, and JRE contains JVM.

One more thing worth knowing. Since Java 11, Oracle and most vendors stopped shipping a separate standalone JRE download. Today you install a JDK, and if you need a small runtime, you create it yourself with jlink.

What Is Inside the JDK

The JDK has three big layers. Here is what each one gives you.

1. The runtime layer

• HotSpot JVM (the engine that runs bytecode and does just-in-time compilation)
• Garbage collectors such as G1, ZGC, and Shenandoah (depends on the vendor build)
• Class libraries (collections, networking, I/O, concurrency, security)

2. The developer tools layer

Tool	Purpose
javac	Compiles .java files into .class bytecode
java	Launches a Java application
jar	Packages classes into a JAR file
javadoc	Generates API documentation from code comments
jshell	Interactive shell for quick experiments
jdb	Command line debugger
jlink	Builds a custom, smaller runtime image
jpackage	Creates native installers (MSI, DMG, DEB)
jcmd, jconsole, jfr	Monitoring, diagnostics, and flight recording
keytool	Manages keys and certificates

3. The supporting files

• Header files for native code (JNI)
• Source for core classes (src.zip)
• Security and configuration files

How the JDK Works Step by Step

Here is the full journey of a simple program.

1. You write HelloWorld.java.
2. javac HelloWorld.java compiles it into HelloWorld.class (bytecode).
3. java HelloWorld starts the JVM.
4. The JVM loads the class, verifies it, and runs it. Hot code paths get compiled to native machine code by the JIT compiler.
5. The garbage collector cleans up unused objects while the program runs.

java

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello from the JDK!");
    }
}

bash

javac HelloWorld.java
java HelloWorld

This "compile once, run anywhere" idea is why Java still powers banking systems, Android apps, big data tools, and enterprise backends in 2026.

JDK Distributions Compared

Here is where people get tripped up. "JDK" is not one single product. Many vendors build and ship their own version from the same open source code (OpenJDK). Most are free.

Distribution	Maintained by	Cost for production	Notes
Oracle JDK	Oracle	Free for latest releases under NFTC, paid subscription for some older versions	Watch the license terms carefully
OpenJDK (builds from openjdk.org)	OpenJDK community	Free	Reference implementation, short update window for non-LTS
Eclipse Temurin	Eclipse Adoptium	Free	Very popular, vendor neutral
Amazon Corretto	Amazon	Free	Long term support, good for AWS
Microsoft Build of OpenJDK	Microsoft	Free	Good fit for Azure workloads
Azul Zulu	Azul	Free community builds, paid support plans	Paid tiers for long support or performance builds
Red Hat build of OpenJDK	Red Hat	Free with RHEL and OpenShift	Enterprise Linux focus

Our take: For most teams, Temurin or Corretto is the safe default. They are functionally close to Oracle JDK, they are free, and you avoid any licensing headaches.

Which JDK Version Should You Use in 2026

Java now ships a new feature release every six months, and a Long-Term Support (LTS) release roughly every two years. As of October 2026, here is where things stand based on Oracle's own download page:

• JDK 27 is the latest release (September 2026). It is not an LTS version.
• JDK 25 is the latest LTS release (September 2025).
• JDK 21 is the previous LTS release.

Version	Type	Free production updates from Oracle until	Good for
JDK 27	Feature release (non-LTS)	March 2027	Testing new features, short-lived projects
JDK 25	LTS	September 2028 (under NFTC)	New production projects
JDK 21	LTS	September 2026 (already ended for Oracle's free terms)	Existing apps that need a planned upgrade
JDK 17	LTS	Subscription needed for Oracle builds	Legacy apps, move to 21 or 25 when possible
JDK 11 and 8	Older LTS	Subscription needed for Oracle builds	Legacy only, plan migration

Practical advice:

• Starting a new project? Use JDK 25.
• Running JDK 21? Its still a solid LTS, but if you use the Oracle build, check your license now, because Oracle's free update window for it ended in September 2026. Community builds like Temurin and Corretto continue to ship updates.
• Do not run production on a non-LTS release unless you are ready to upgrade every six months.

How to Install and Check JDK

Check if JDK is already installed

bash

java -version
javac -version

If java -version works but javac -version says "command not found", you have a runtime without the compiler.

Install steps (general)

1. Choose a distribution (Temurin or Corretto is a safe pick).
2. Download the installer for your OS (Windows, macOS, Linux).
3. Run the installer, or use a package manager:

bash

# macOS (Homebrew)
brew install --cask temurin

# Ubuntu / Debian
sudo apt install openjdk-25-jdk

# Windows (winget)
winget install EclipseAdoptium.Temurin.25.JDK

4. Set JAVA_HOME to the JDK folder and add bin to your PATH.
5. Run java -version and javac -version again to confirm.

Package names change between releases, so verify the exact name on your distro before running these.

What is JAVA_HOME?

JAVA_HOME is an environment variable that points to your JDK install folder. Build tools like Maven, Gradle, and IDEs read it to find the right Java. If your build uses the wrong Java version, this is the first thing to check.

JDK Cost: Is It Really Free?

Short answer: the JDK itself can be completely free, but only if you choose the right build and the right version. Let us look at the numbers, and then think about whether they make sense.

The free options

• OpenJDK builds, Temurin, Corretto, Microsoft Build, and Azul Zulu community builds cost $0 for production use.
• Oracle JDK 25 and the latest feature releases are free for production under the Oracle No-Fee Terms and Conditions (NFTC). Oracle states JDK 25 gets updates under NFTC until September 2028. After that, updates move to the OTN license, where production use beyond limited free grants needs a fee.

The paid option: Oracle Java SE Universal Subscription

Since January 2023, Oracle sells Java through a per-employee subscription. This is the part that surprises people, because it counts your entire workforce, not just the developers who touch Java.

I checked this against several sources. One published price tier table (from ServiceNow's documentation, updated March 2026) lists these monthly rates per employee, and other licensing advisory sites report the same starting rate of $15.

Total employees	List price per employee per month	Example annual cost at that size
1 to 999	$15.00	500 employees: $90,000
1,000 to 2,999	$12.00	1,000 employees: $144,000
3,000 to 9,999	$10.50	3,000 employees: $378,000
10,000 to 19,999	$8.25	10,000 employees: $990,000
20,000 to 29,999	$6.25	20,000 employees: $1,500,000
30,000 to 39,999	$5.70	30,000 employees: $2,052,000
40,000 to 49,999	$5.25	40,000 employees: $2,520,000

Annual cost = employees x monthly rate x 12. These are list prices. Real deals are negotiated, and some advisory sites report discounts of 30 to 60 percent, but those numbers come from firms that sell negotiation services, so treat them as claims to verify, not promises.

A discrepancy we found while verifying: one site claimed a 5,000 employee company would pay about $315,000 per year by using the $5.25 rate. That does not match the tier table above. A 5,000 employee company falls in the 3,000 to 9,999 band at $10.50, which works out to roughly $630,000 per year at list. Always calculate from the official tier, not from a blog headline.

Also note that contractors and part-time staff can count toward "employees" under Oracle's broad definition, and some sources mention annual price escalation clauses of around 8 percent. Check your own contract for this, we could not confirm it from Oracle's public pages.

Is that price actually good? Let us think technically

Short answer: for most companies, no. Here is the reasoning.

1. You pay for headcount, not usage. A 500 person company with 20 Java developers pays $90,000 per year. That is $4,500 per Java developer per year for a runtime that has free, production grade alternatives built from the same source code.
2. The free builds are technically equivalent for most workloads. Temurin, Corretto, and Zulu pass the same compatibility tests (TCK). Your Spring Boot, Jakarta EE, or Kafka app will not behave differently.
3. What you actually buy from Oracle is vendor support, access to older versions' patches (like Java 8 until at least December 2030 and Java 11 until at least January 2032 for subscribers), and legal certainty if you are standardised on Oracle products.
4. Where it can make sense: you run legacy Java 8 or 11 you cannot migrate soon, you are deep in the Oracle stack already, or your auditors require a single named vendor.
5. Where it rarely makes sense: greenfield projects, startups, SaaS companies, and any team that can run JDK 25 on a free distribution.

Verdict: The per-employee metric makes Oracle's subscription expensive for companies with a large non-technical workforce. If your Java footprint is small compared to your headcount, switching to a free distribution is usually the better financial and technical call. Paying makes sense only if you need the specific support and patch guarantees.

Cost comparison at a glance

Option	License cost	Support	Best for
Eclipse Temurin	$0	Community (paid support available from partners)	Most teams
Amazon Corretto	$0	Community / AWS	AWS workloads
Azul Zulu	$0 community, paid plans for support	Commercial option	Teams wanting paid support without Oracle
Oracle JDK 25 (NFTC)	$0 until Sept 2028	Limited	New projects on latest LTS
Oracle Java SE Subscription	$5.25 to $15 per employee per month at list	Oracle support	Legacy Java 8 / 11, Oracle shops

Java Development Cost: What You Pay for People, Not the Kit

Here is the thing. The JDK is rarely your biggest Java expense. The developers are. Whether you are hiring in-house or outsourcing, rates vary a lot by region.

Region	Typical hourly rate (USD)	Monthly at 160 hours
United States	$60 to $150+	$9,600 to $24,000+
Western Europe	$50 to $120	$8,000 to $19,200
Eastern Europe	$30 to $70	$4,800 to $11,200
Latin America	$25 to $70	$4,000 to $11,200
India	$20 to $50	$3,200 to $8,000
Southeast Asia	$20 to $45	$3,200 to $7,200

Source: regional ranges from Flexiple's 2026 Java hiring guide. Another 2026 dataset (Second Talent) puts mid-level India rates at $20 to $52 per hour, which is consistent. Monthly figures are our arithmetic.

Is the lower rate really cheaper? Not always. A low hourly rate can cost more if the developer is junior for a complex architecture, if time zone gaps slow down decisions, or if there is no code review process. A simple way to judge it is cost per delivered feature, not cost per hour.

Quick illustration: A team of 3 mid-level Java developers at a blended $35 per hour working full time costs about 3 x 160 x $35 = $16,800 per month. Over six months that is about $100,800, before project management, QA, and cloud costs. If you want a project specific estimate, try our software development cost calculator.

Common JDK Mistakes (and How to Avoid Them)

• Installing a JRE and wondering where javac went. Install a JDK.
• Mixing Java versions. Your IDE uses 25, your build server uses 17, and you get strange errors. Pin the version in your build file.
• Running Oracle JDK without reading the license. Teams often forgets this until an audit letter arrives. Prefer a free distribution unless you have a reason.
• Using a non-LTS version in production and then missing the six month upgrade window.
• Ignoring security updates. Patch your JDK like you patch your OS.
• Wrong JAVA_HOME. Check it first when a build fails after an upgrade.

Digisoft Solution Java Development Services

Knowing what the JDK is gets you started. Building a secure, scalable Java product is a different job, and that is where an experienced team saves you months. At Digisoft Solution, we have been delivering custom software for over 13 years, and Java is part of the backend stack our engineers work with alongside .NET, Node.js, Python, and PHP.

What we can help you with

• Custom Java application development for enterprise, SaaS, and internal business systems. See our software development services and enterprise application development.
• Backend and API development with REST APIs, integrations, and secure data layers. Explore backend development, API development, and API integration.
• Legacy modernization, including moving old Java 8 or 11 systems to JDK 25 and a free, supported distribution. This is exactly where license costs get cut. See legacy application modernization.
• Cloud migration and cloud-native builds on AWS, Azure, and Google Cloud, using cloud migration services and cloud application development.
• Android application development, where Java skills still matter. Visit Android app development.
• Testing and QA for performance, security, and API layers through our software testing services.
• Technology consulting, such as picking the right JDK distribution and version for your stack, through software consulting and IT consulting.

Flexible ways to work with us

Model	Best for	Learn more
Dedicated team	Long term product roadmaps	Hire dedicated developers
Staff augmentation	Filling skill gaps fast	Staff augmentation
Offshore development	Cost efficient delivery	Offshore software development
Fixed price or time and materials	Defined scope vs evolving scope	Contact us

See how we deliver

Our backend and platform work spans industries like banking, healthcare, and fintech. A few examples from our case studies (note these specific projects used .NET, and they show how we handle architecture, APIs, and scale):

• Vision Care Direct SaaS platform: member onboarding cut from 2 to 3 days to under 30 minutes, and payment errors reduced from 8% to under 1%.
• Veridian Urban Systems smart city platform: concept to launch in eight months, with reporting time reduced by 60%.

Want a quick opinion on your Java stack or license exposure? Book a free consultation and we will give you a clear technical roadmap. You can also read more engineering guides on our blog.

People Also Ask

These are the questions people type into Google and AI assistants most often about the JDK.

What is JDK used for?

JDK is used to develop Java applications. It compiles source code into bytecode, packages applications, generates documentation, debugs programs, and monitors performance.

What is the difference between JDK and SDK?

SDK (Software Development Kit) is a general term for any toolkit used to build software for a platform. JDK is the specific SDK for the Java platform. So every JDK is an SDK, but not every SDK is a JDK.

What is the difference between JDK and JDE or an IDE?

A JDK provides the compiler and tools. An IDE such as IntelliJ IDEA, Eclipse, or VS Code is the editor where you write code. The IDE uses the JDK behind the scenes.

Is JDK the same as Java?

Not exactly. Java is the programming language and platform. The JDK is the toolkit you install to develop in that language.

Which is better, Oracle JDK or OpenJDK?

Technically they are very close, since Oracle JDK is built from OpenJDK source. For most teams, a free OpenJDK build like Temurin or Corretto is the better choice because there is no per-employee licensing risk.

Can I run Java without installing the JDK?

Yes, if you only run a Java app and have a runtime (or the app bundles one). You need the JDK only to compile or build.

Is Java still worth learning in 2026?

Yes. Java remains a core language for enterprise backends, banking, Android, and large scale systems, and the six month release cycle keeps adding modern features.

Does JDK include a JRE?

Yes, the JDK includes everything needed to run Java programs. In modern versions (Java 11 and above) there is no separate JRE download, and you can generate a slim runtime with jlink.

How much does the JDK cost?

For most use cases, $0. Free builds exist from Eclipse Temurin, Amazon Corretto, Microsoft, Azul, and Oracle (for recent releases under NFTC). Paid cost applies mainly to Oracle's Java SE Universal Subscription, listed at $5.25 to $15 per employee per month.

FAQ

1. What does JDK stand for?

JDK stands for Java Development Kit.

2. What is the latest JDK version?

As of October 2026, JDK 27 is the latest release, and JDK 25 is the latest Long-Term Support (LTS) release, according to Oracle's download page.

3. Which JDK version is best for beginners?

JDK 25 (LTS). It is stable, supported for years, and includes modern language features.

4. Is JDK free for commercial use?

Yes, if you use a free distribution such as Temurin, Corretto, or Microsoft Build of OpenJDK. Oracle JDK 25 is also free for production under NFTC until September 2028. Older Oracle JDK versions may need a paid subscription.

5. What is the Oracle Java SE Universal Subscription?

It is Oracle's paid Java license, priced per employee per month across your whole organization. List prices run from $15 for small companies down to $5.25 for very large ones.

6. Do contractors count as employees for Oracle Java pricing?

Oracle's definition is broad and can include contractors and part-time staff, so confirm with Oracle in writing before you sign.

7. What is an LTS version of Java?

LTS means Long-Term Support. These versions (8, 11, 17, 21, 25) get security and bug fix updates for many years, which makes them the right choice for production.

8. What is the next LTS release after JDK 25?

Based on the two year LTS cadence, the next LTS is expected in September 2027. Always confirm on the official OpenJDK or Oracle roadmap.

9. How do I know which JDK my project is using?

Run java -version and javac -version in your terminal, and check the JAVA_HOME variable and your build file (pom.xml or build.gradle).

10. Can I have multiple JDK versions on one machine?

Yes. Tools like SDKMAN, jEnv, or your IDE settings let you switch between versions per project.

11. How much does it cost to hire a Java developer?

Rates run roughly $20 to $50 per hour in India and Southeast Asia, $30 to $70 in Eastern Europe, and $60 to $150+ in the United States, depending on seniority and skills.

12. How can Digisoft Solution help with Java projects?

We offer Java backend development, API integration, legacy modernization, cloud migration, QA, and dedicated developers. Talk to our team for an estimate.

Final Thoughts

The JDK is the foundation of every Java project, and in 2026 the practical advice is simple:

• Use JDK 25 (LTS) for new work.
• Pick a free distribution like Temurin or Corretto unless you have a clear reason to pay.
• Read license terms before using any Oracle build in production, because the per-employee model can turn a "free" tool into a six or seven figure line item.
• Remember that people cost more than the kit, so spend your budget on the right engineers and architecture.

If you want help choosing the right stack, modernizing an older Java system, or building a new product, get in touch with Digisoft Solution.