Common JDK 9 Setup Issues and How to Fix Them

PerformanceTroubleshootingException-HandlingJVMJava-EE
Snippet of programming code in IDE
Published on

Common JDK 9 Setup Issues and How to Fix Them

Java Development Kit (JDK) 9 marked a significant advancement in the Java world, introducing features like the Java Platform Module System (JPMS). However, during the installation or setup process, many users encounter common issues. In this blog post, we will explore these issues and provide solutions for a smooth JDK 9 experience.

Table of Contents

  1. Common Setup Issues
  2. Fixing Setup Issues
  3. Conclusion

Common Setup Issues

Installation Doesn't Proceed

One of the primary issues users report is that the installation process stalls or fails outright. This can result from several factors, such as conflicting applications or insufficient system permissions.

How to fix it:

  • Ensure that you download the correct installer for your operating system from the official Oracle JDK website.
  • Run the installer as an administrator.
  • Temporarily disable antivirus software that might be interfering with the installation.

Environment Variables Not Set

Once JDK 9 is installed, many users find that their system is not recognizing the Java commands. This is typically due to the JAVA_HOME environment variable not being set or added to the system PATH.

How to fix it:

  • Set the JAVA_HOME variable to point to the JDK installation directory.

Windows:

  1. Right-click on Computer and select Properties.
  2. Click on Advanced system settings.
  3. Click on Environment Variables.
  4. Under System Variables, click New and set:
    • Variable name: JAVA_HOME
    • Variable value: C:\Program Files\Java\jdk-9
  5. Append JDK to the PATH variable:
    • Find the Path variable, click Edit, and add: %JAVA_HOME%\bin.

Linux/Mac: Open your terminal and add the following lines to your .bashrc or .bash_profile:

export JAVA_HOME=/usr/lib/jvm/java-9-openjdk-amd64
export PATH=$JAVA_HOME/bin:$PATH

Then run source ~/.bashrc.

Incompatibility with Existing Java Versions

Installing JDK 9 alongside older versions can lead to conflicts, especially with establishing default Java versions for your system.

How to fix it:

  • Remove older Java versions using your operating system’s package manager.

For Windows:

  • Go to Control Panel > Programs > Programs and Features and uninstall previous Java versions.

For Linux:

sudo apt-get remove openjdk-* 
sudo apt-get autoremove

IDE Integration Problems

Sometimes, after installing JDK 9, users may face compilation issues within their integrated development environments (IDEs) such as Eclipse or IntelliJ IDEA. The IDE may not recognize JDK 9 as a valid SDK.

How to fix it:

  • Update the IDE to the latest version, as older versions may not support JDK 9.
  • Within your IDE settings, configure the JDK path to the installed JDK 9 directory.

For IntelliJ IDEA:

  1. Go to File > Project Structure.
  2. Under SDKs, click the "+" button and select JDK, navigating to your JDK 9 installation folder.

For Eclipse:

  1. Go to Window > Preferences > Java > Installed JREs.
  2. Click Add, select Standard VM, and then point to your JDK 9 installation.

Fixing Setup Issues

Detailed Solutions

Now that we covered the common issues, let's dive deeper into the fixes with practical code snippets and operational tweaks.

Verifying the Installation

After setting your JAVA_HOME and updating your PATH, it’s essential to verify that JDK is installed correctly.

Open your command-line interface and run:

java -version

You should see output like:

java version "9.0.4" 
Java(TM) SE Runtime Environment (build 9.0.4+11)
Java HotSpot(TM) 64-Bit Server VM (build 9.0.4+11, mixed mode)

If you did not get this output, revisit the installation steps or check the environment variable settings.

Using JShell

JDK 9 introduced JShell, a Read-Eval-Print Loop (REPL) tool that allows you to execute Java code snippets interactively. If you suspect your installation is problematic, using JShell can help you troubleshoot.

To launch JShell:

jshell

You can try simple commands to see if Java responds as expected:

System.out.println("Hello, JDK 9!");

Modules and JPMS

One significant feature introduced in JDK 9 is the Java Platform Module System (JPMS). If bytecode targeting or module-related issues arise, here's how to create and run a simple module.

Create a project directory:

mkdir sample.module
cd sample.module
mkdir module-info.java src

Create a module-info.java file:

module my.module {
    exports com.myapp;
}

Create MyApp.java inside src/com/myapp:

package com.myapp;

public class MyApp {
    public static void main(String[] args) {
        System.out.println("Welcome to JDK 9 Modules!");
    }
}

Compile and run your module:

javac -d out --module-source-path src $(find src -name "*.java")
java --module-path out -m my.module/com.myapp.MyApp

A Final Look

Encountering issues during the JDK 9 setup is common but usually solvable. By understanding the root of these issues, whether it's installation failure, environment variable mishaps, version incompatibility, or IDE integration, you can easily troubleshoot your way to success.

By following the detailed solutions provided, you should be able to set up JDK 9 confidently and take full advantage of its powerful features, including modules and JShell for interactive programming.

For additional resources, check the Oracle Java Documentation to dive deeper into JDK 9's capabilities.

Feel free to leave your comments or questions below if you face any other setup issues. Happy coding!