How to Check JDK Version

In this blog post, we will delve into the topic of how to check JDK version. Understanding which version of the Java Development Kit (JDK) you are using is crucial for ensuring compatibility with your projects and leveraging the latest features and security updates. This guide will walk you through the process step by step, covering both basic and advanced methods.

Understanding the Concept

The Java Development Kit (JDK) is a software development environment used for developing Java applications. It includes the Java Runtime Environment (JRE), an interpreter/loader (Java), a compiler (javac), an archiver (jar), a documentation generator (Javadoc), and other tools needed for Java development. Knowing the version of JDK installed on your system is essential, as different projects may require different versions of the JDK.

Practical Implementation

Using Command Line

The most straightforward way to check your JDK version is through the command line. This method works across different operating systems, including Windows, macOS, and Linux.

Open your command line interface (CLI) and type the following command:

java -version

This command will display the installed JDK version. For example:

java version "1.8.0_281"
Java(TM) SE Runtime Environment (build 1.8.0_281-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.281-b09, mixed mode)

In this example, the JDK version is 1.8.0_281.

Using the System Properties

Another way to check the JDK version is by using a simple Java program to print out the system properties. Create a new Java file (e.g., CheckJDKVersion.java) and include the following code:

public class CheckJDKVersion {
    public static void main(String[] args) {
        System.out.println("JDK Version: " + System.getProperty("java.version"));
    }
}

Compile and run the program:

javac CheckJDKVersion.java
java CheckJDKVersion

This will output the JDK version:

JDK Version: 1.8.0_281

Common Pitfalls and Best Practices

Common Mistakes

• Not Setting JAVA_HOME: Many developers forget to set the JAVA_HOME environment variable, which can lead to issues when running Java applications or build tools like Maven or Gradle.
• Multiple JDK Versions: Having multiple JDK versions installed can cause confusion and conflicts. Ensure you are using the correct version for your project.
• Ignoring Updates: Using outdated JDK versions can expose your applications to security vulnerabilities. Always try to use the latest stable version.

Best Practices

• Set JAVA_HOME: Always set the JAVA_HOME environment variable to point to your JDK installation directory.
• Use Version Managers: Consider using version managers like SDKMAN! for Unix-based systems or jEnv for managing multiple JDK installations.
• Regular Updates: Keep your JDK updated to benefit from the latest features and security patches.

Advanced Usage

For advanced users, there are additional tools and methods to manage and check JDK versions.

Using SDKMAN!

SDKMAN! is a tool for managing parallel versions of multiple Software Development Kits (SDKs) on Unix-based systems. To check the installed JDK versions using SDKMAN!, follow these steps:

# Install SDKMAN!
curl -s "https://get.sdkman.io" | bash

# Install a specific JDK version
sdk install java 11.0.9.hs-adpt

# List installed JDK versions
sdk list java

This will display all the JDK versions installed via SDKMAN! and allow you to switch between them easily.

Using jEnv

jEnv is another tool for managing multiple Java environments on a single system. To check and switch between JDK versions using jEnv, follow these steps:

# Install jEnv
brew install jenv

# Add a JDK to jEnv
jenv add /Library/Java/JavaVirtualMachines/jdk-11.0.9.jdk/Contents/Home/

# List all JDK versions managed by jEnv
jenv versions

With jEnv, you can easily switch between different JDK versions for different projects.

Conclusion

In this blog post, we covered how to check JDK version using various methods, including the command line, system properties, and advanced tools like SDKMAN! and jEnv. Understanding and managing your JDK version is essential for ensuring compatibility and leveraging the latest features and security updates. By following the best practices and avoiding common pitfalls, you can streamline your Java development workflow and maintain a robust development environment.