Even a Linux novice can understand it in seconds! Easily check which JDK versions are installed on your Linux system

As a Linux system administrator or developer, being familiar with the method of checking the Java Development Kit (JDK for short) version will be of great benefit to your work progress. With a series of efficient commands and operating procedures, you can easily grasp the version information of the JDK installed in the Linux system. This article will provide a detailed analysis of querying and confirming the selected JDK version in the Linux environment, displaying a list of all installed JDKs, and the specific steps for setting and converting different versions of JDK.

1. Check the default JDK version

In Linux environments, OpenJDK is often pre-installed as the default Java development kit. If you want to know the JDK version installed by default on the system, you can use the following related commands to check:

bash
java -version

Execute this commandHow to check jdk version in linux, it will reveal the default JDK version information installed in the system, detailing relevant details such as version number and publisher. With the help of this command, you can quickly grasp the required Java usage environment information.

In addition, you can also view the information of the Java compiler in the system through the following command:

javac -version

This command can view the Java compiler (javac) model information loaded on the system. For developers, familiarity with the compiler model is also critical.

2. View all installed JDK versions

In addition to querying the default JDK version, sometimes it is also necessary to know all JDK versions installed in the system. You can obtain relevant information by following the steps below:

-Please enter the following command in the terminal environment to inventory all installed Java-related software packages:

Update Java option configuration

After executing this command, you will see a list of all installed JAVA packages in the current system and can choose which one becomes the default setting.

You can use the following commands to dig deeper into the various Java compiler software packages installed on the system.

Enable javac configuration options: update-alternatives --config javac.

This will allow you to list all loaded Java compilers and select the required version.

Through the above steps, you will be able to fully grasp all version information of the JDK and compilers installed in the system, and make timely replacements and settings adjustments.

3. Set up and switch different versions of JDK

During the project development stage, it is necessary to use multiple versions of Java Development Kit (JDK for short) to ensure accurate testing and compatibility. On the Linux operating system, you can use the 'update-alternatives' command to easily achieve flexible conversion between various JDK versions. This process will be explained to you in detail below:

- Use the following command to list the available Java package options:

Use "sudo" to run the command "update-alternatives --config java"

With this command, you can choose which Java package to use as the default.

In addition, you can also use the following instructions to select the JAVA compiler component.

Execute the following command to change the configuration of the Java compiler: sudo update-alternatives --config java

This allows you to flexibly set and switch different versions of JDK and compilers.

Some Linux versions are equipped with special tools and programs to achieve flexible management and switching of different JDK versions. For example, the Ubuntu platform has update-java-alternatives, a utility tool for optimizing Java software programs.

4. Check environment variables

In a Linux system environment, it is usually necessary to check the correctness of the JAVA_HOME environment variable to avoid running problems. This variable points to the specific installation path of Java, so it is crucial for various applications and development tools. After the following steps, you can verify whether the JAVA_HOME you set is correct:

echo $JAVA_HOME

If the correct Java installation path is returned as expected, then we can be sure that the JAVA_HOME environment variable has been successfully set. If nothing can be read, the variable needs to be configured manually.

5. Use alternatives command management

In the Linux operating system, the alternative tool (Alternatives) provides great convenience for managing various available options (such as various software versions, etc.). With this command, you can quickly and accurately manage and switch the settings or parameters associated with each software.

For example, in the case of the updated Java standard software packageHow to check the jdk version in linux, the application of the update-alternatives command can be seen. Likewise, it can also play a significant role in other software service environments.

6. Find and download the JDK that suits your needs

When necessary, in addition to the JDK that comes with the operating system or is officially recommended by the manufacturer, you may wish to download the corresponding version or JDK launched by other companies according to the special requirements of the project. These can be found and downloaded by visiting the Oracle official website, OpenJDK official website or other third-party websites.

Before downloading linux ftp, please carefully select the appropriate JDK version according to your own system and its actual needs (such as development/test/production environment, etc.), and strictly follow the official instructions for the corresponding download and installation process.

7. Update and upgrade JDK

With the passage of time and the development of technology, various softwares continue to launch new versions to correct bugs, expand functions and improve operating efficiency. Therefore, in practical operation, it is necessary to regularly review and upgrade the JDK version installed.

In the Linux environment, updating/upgrading the Java Development Kit (JDK) is usually implemented through the package management tools that come with the distribution (such as apt, yum, etc.). The specific operations vary depending on the release version. Usually you only need to run the corresponding instructions to complete the upgrade process.

In short, the ability to detect, manage and adjust the Java Development Kit (JDK) on a Linux system is undoubtedly one of the skills that developers and managers must master and use proficiently. With the help of the strategies and operating procedures described in this article, the author firmly believes that you will be able to complete tasks such as JDK version information query, switching, and environment configuration with ease, thereby promoting various development work more efficiently.

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