Checking java version installed

How can I tell what version of Java I have installed?

I want to start toying around with java (eventually getting to the point where I can write basic little programs for android or web), but I’ve managed to have java messed up on my computer (from past experiments). I’m not sure which version of java I have, and would like to know if there is a command to see the version of java that is installed and active. Also, which version works best? All this on 32bit Ubuntu 12.04 EDIT:
Ok, so it seems like I have both openjdk 6 and 7, with openjdk 7 in use. I want to use openjdk 7, so how do I uninstall openjdk 6? Is just via USC good enough or is there a command that should be run?

4 Answers 4

update-java-alternatives -l shows you all the Java versions you have installed.

java -version shows you the Java version you are using.

java -showversion shows you the Java version you are using and help.

Normally it would be OpenJDK.

This command should tell you what is currently providing the Java virtual machine ( java ) and the Java compiler ( javac ):

file /etc/alternatives/java /etc/alternatives/javac 

This assumes the «alternatives» system is working properly, which might not be the case, depending on how Java has been «messed up» in the past. To check this, run:

If the alternatives system is working correctly and being used by Java, then you should see:

/usr/bin/java: symbolic link to `/etc/alternatives/java' /usr/bin/javac: symbolic link to `/etc/alternatives/javac' 

Otherwise please edit your question to provide details. Then it should be possible to give a more specific answer.

You can remove openjdk-6 with the Software Center. There are multiple packages associated with it, so you may need to remove more than one packages. (All the `openjdk-6 packages are listed here.)

Or you can use the command-line:

sudo apt-get remove openjdk-6-\* icedtea-6-\* 

However, whichever method you use, you may want to check first to see what depends on these packages—you might have software installed that specifically needs version 6. (Probably not, but possibly.)

You can check for this by simulating the removal operation on the command-line:

apt-get -s remove openjdk-6-\* icedtea-6-\* 

This will show you the effects of removing those packages, including what other packages would be removed as well. (You’ll notice that since this is a simulation, you don’t need sudo .)

If you want to be able to continue using Java content online in your web browser (this is not the same thing as JavaScript), then before you remove any icedtea-6- or openjdk-6- packages (except perhaps openjdk-6-jdk ), you should make sure you have icedtea-7- packages installed corresponding to whatever icedtea-6- packages are installed.

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How to Check Java Version

In today’s blog, we will be showing you how to check the Java version on Windows and macOS operating systems.

List of content you will read in this article:

Among all the programming languages, Java is considered to be the most commonly used language that has been adopted worldwide. There are numerous reasons why Java has gained popularity over other alternatives. There is no doubt that Java has been famous among all Fortune 500 companies and is widely recommended by developers. Its user-friendly and flexible nature makes it a go-to programming language for web developers and programmers.

The main reasons behind Java being popular is its fast speed, high-end security, and reliability. Along with such benefits, Java also offers private transmission, automatic memory management, and secure crucial information.

About Java

Introduced in the 1990s by James Gosling, Java is an object-oriented, robust, and secure programming language. The team started this Java project to develop a language suitable, especially for digital devices like set-top boxes, television, etc. At first, C++ was to be used in the Java project but was not considered for some reasons. Later, Gosling expanded C++ and led to another stage of a project Green, which was later renamed the ‘Greentalk’ project by Gosling and his team members. These project files had the file extension as .gt, which is later recognized as ‘OAK.’

The name ‘OAK’ was given to the project after an oak tree that was located outside Gosling’s office. But later on, the term ‘OAK’ was changed to Java. After various talks and brainstorming sessions, Gosling and his team come to multiple names- JAVA, DNA, SILK, BURY, etc. Still, they decided on JAVA after many discussions due to its uniqueness. This name (Java) comes up from a type of espresso bean. Gosling and his team members had come up with this name while having a cup of coffee near their office.

The main principles on which Java was built are- robust, portable, platform-independent, multi-thread, etc. In 1995, Java was recognized as one of the ten best products in Time magazine. Today, Java has been used in various fields like internet programming, mobile devices, games, etc. later, multiple versions of Java have been introduced over the years with new added features and functionalities.

Versions of Java

Over time, Java has introduced various versions with different and advanced features than the earlier version. Every version has fulfilled the drawback of their previous versions. Some of the versions are still supported, and some of them are not. Below is the list of all the Java versions introduced to date.

Support Until

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How to Check Java Version Installed on Linux

How do I check my current Java version? There are several ways to check if Java is installed and which version is running on your system.

In this tutorial, learn how to check the Java version installed on Linux distros, including Ubuntu, CentOS, and Debian.

• A user account with sudo privileges
• Access to the command-line/terminal window
• A version of Java

Method 1: Check the Java Version On Linux

To check the Java version on Linux Ubuntu/Debian/CentOS:

2. Run the following command:

3. The output should display the version of the Java package installed on your system. In the example below, OpenJDK version 11 is installed.

Note: If the output indicates there is no such package on the system, you can install it with the help of one of our guides – How to install Java on Ubuntu or How to Install Java on CentOS.

You can also check the version of the primary Java compiler – javac (pronounced “java-see”) with the command:

Method 2: Find Version by Checking Path Where Java is Installed

There are two ways to find the path of the Java directory.

The first option includes running a single command:

update-alternatives --list java

The system should respond with the path where Java is installed.

Note: This option may not work on CentOS systems. If you have issues finding the path of the Java directory with the command above, use the alternative outlined below.

Alternatively, you can use the whereis command and follow the symbolic links to find the Java path.

The output tells you that Java is located in /usr/bin/java.

2. List the content of the /usr/bin/java directory:

Inspecting the directory shows that /usr/bin/java is only a symbolic link for /etc/alternatives/java.

3. Just like in the previous step, list the content of the provided path by running:

Finally, the output displays /etc/alternatives/java is another symbolic link and that the real path of the Java directory is /usr/lib/jvm/java-11-openjdk-amd64/bin/java.

Method 3: Search for Java in the Installed Packages List

You can also prompt the system to list installed packages and search for Java, with its version number.

Find Java by listing all installed packages.

1. To generate a list of all installed packages, use the command:

2. Scroll up/down until you find the Java packages as shown in this example.

To avoid searching through all installed packages, list Java packages only. Prompt the system to list a specific software package. In this case, the package name is openjdk:

sudo apt list --installed | grep -i openjdk

Note: CentOS users need to modify the commands for listing installed packages for their package manager. Use the commands: sudo yum list installed and sudo yum list installed | grep -i openjdk instead.

With this article, you have successfully checked the Java version installed on Linux. We also covered checking the Java path and searching for Java among the installed packages.

Once the Java version is confirmed, you can start developing anything from lightweight mobile to desktop applications.

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How to Check Java Version on Mac or Windows

Java runs many of the applications that we use daily. Many applications cannot run on older versions of Java. Hence, it is essential to know which version is installed on your system.

In this tutorial, learn how to check the Java version on your Mac or Windows system.

• A system running macOS or Windows
• Access to the command-line/terminal window
• A version of Java installed

Check Java Version on Mac

You can find the version of Java on macOS by:

• using the GUI (Mac’s System Preferences)
• prompting for the version in the terminal window

Option 1: Check Java Version on Mac Using the GUI

To check the Java version on Mac without using the terminal by searching for the Java Control Panel in the System Preferences.

1. Click the Apple icon in the menu bar to open the drop-down menu and navigate to System Preferences.

2. A new window opens with various icons and settings. Find and click the Java icon to open the Java Control Panel.

3. Once the Java Control Panel opens, click the About button. A new window with Java version information should appear.

Option 2: Check Java Version on Mac Using the Terminal

If you prefer using the terminal, checking the Java version is a simple one-command process.

1. First, open the terminal. To do so, click the Spotlight Search button in the top-right of the screen.

2. Type terminal in the search bar and open it by clicking on the icon in the search results.

3. Once in the command line, run the command: java -version . The output should display the Java version installed on your MacOS.

To check the version of the primary Java compiler – javac (pronounced “java-see”) use the command:

Note: If you have a Linux system, refer to How To Check Java Version Installed On Linux.

Check Java Version on Windows

To check the Java version on a Windows computer, you can use:

Option 1: Check Java Version on Windows Using GUI

To find the Java version on your Windows without opening a terminal window, use the Control Panel.

1. Open the Windows menu in the bottom-left corner and type control panel in the search bar.

2. Find the Control Panel in the search results and click the icon to open it.

3. Move to the Programs directory.

4. Find and click the Java icon to open the Java Control Panel.

5. Once the control panel opens, click the About button.

6. The About Java window should appear and display the Java version on your computer.

Option 2: Check Java Version on Windows Using Command Line

Another option to find the Java version on Windows is through the command line.

1. Open the Windows Start menu in the bottom-left corner and type cmd in the search bar.

2. Then, open the Command Prompt once it appears in the search results.

3. A new window with the command prompt should appear. In it, type the command java -version and hit Enter. The output should display the Java version installed on your Windows system.

You can also check the version of the Java’s primary compiler, javac, with the command:

This article showed you how to check the version of Java installed on a macOS or Windows system.

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