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选题[tech]: 20210911 How to Set JAVA_HOME Variable in Ubuntu Linux Correctly
sources/tech/20210911 How to Set JAVA_HOME Variable in Ubuntu Linux Correctly.md
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[#]: subject: "How to Set JAVA_HOME Variable in Ubuntu Linux Correctly"
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[#]: via: "https://itsfoss.com/set-java-home-ubuntu/"
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[#]: author: "Abhishek Prakash https://itsfoss.com/author/abhishek/"
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[#]: collector: "lujun9972"
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[#]: translator: " "
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[#]: reviewer: " "
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[#]: publisher: " "
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[#]: url: " "
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How to Set JAVA_HOME Variable in Ubuntu Linux Correctly
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======
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If you are [running Java programs on Ubuntu][1] using Eclipse, [Maven][2] or Netbeans etc, you’ll need to set JAVA_HOME to your path. Otherwise, your system will complain that “java_home environment variable is not set”.
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In this beginner’s tutorial, I’ll show the steps to correctly set Java Home variable on Ubuntu. The steps should be valid for most other Linux distributions as well.
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The process consists of these steps:
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* Making sure Java Development Kit (JDK) is installed.
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* Finding the correct location of JDK executable.
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* Setting the JAVA_HOME variable and making the change permanent.
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### Step 1: Check if JDK is installed
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The simplest way to check if Java Development Kit (JDK) is installed on your Linux system is by running this command:
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```
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javac --version
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```
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The above command checks the version of Java compiler. If it is installed, it will show the Java version.
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![Java Compiler is installed][3]
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If the command shows an error like javac command not found, you’ll have to install JDK.
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![Java Compiler is not installed][4]
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If Java Compiler is not installed on your system, install Java Development Kit using this command:
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```
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sudo apt install default-jdk
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```
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This will install the default Java version in your current Ubuntu version. If you need some other specific Java version, you’ll have to specify it while [installing Java on Ubuntu][5].
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Once you have made sure that Java Compiler is present on your system, it’s time to find its location.
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### Step 2: Get the location of JDK executable (Java Compiler)
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The executable is usually located in the /usr/lib/jvm directory. I won’t left you on your own for a guessing game. Instead, let’s find out the path of the Java executable.
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[Use the which command][6] to get the location of Java Compiler executable:
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```
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which javac
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```
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The problem here is that the location it gives is actually a [symbolic link][7]. You’ll have to follow it a couple of times:
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![][8]
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An easier method is to follow the symbolic link and get to the actual executable file directly using this command:
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```
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readlink -f `which java`
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```
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The readlink command follows a symbolic link. I have used ` around _which java_. This is called command substitution and it replaces the command with its output. So basically, the above command is equivalent to _readlink -f /usr/bin/java_ in this case.
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In my example, the location of the executable file is **/usr/lib/jvm/java-11-openjdk-amd64/bin/java**. It could be different for you. Copy the correct path you got from the above command in your system. You know, you can [copy paste in the Ubuntu terminal][9].
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### Step 3: Setting JAVA_HOME variable
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Now that you have got the location, use it to set the JAVA_HOME environment variable:
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```
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export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64/bin/java
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```
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Check the value of JAVA_HOME directory:
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```
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echo $JAVA_HOME
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```
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![][10]
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Try to run your program or project in the SAME TERMINAL and see if it works.
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This is not over yet. The JAVA_HOME variable you just declared is temporary. If you close the terminal or start a new session, it will be empty again.
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To set JAVA_HOME variable ‘permanently’, you should add it to the bashrc file in your home directory.
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You can [use the Nano editor for editing files in the Linux terminal][11]. If you do not want that and take a simple copy-paste approach, use the following commands:
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Back up your bashrc file (in case you mess it, you can get it back):
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```
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cp ~/.bashrc ~/.bashrc.bak
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```
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Next, [use the echo command to append][12] the export command you used at the beginning of this section. _**Change the command below to use the correct path as displayed by your system in**_.
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```
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echo "export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64/bin/java" >> ~/.bashrc
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```
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Verify that it has been correctly added to the end of the file:
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```
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tail -3 ~/.bashrc
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```
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The above [tail command][13] will show the last 3 lines of the specified file.
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Here’s the entire output of the above three commands.
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![][14]
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Now, even if you exit the session or restart the system, the JAVA_HOME variable will still be set to the value you specified. That’s what you want, right?
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Do note that if you change the default Java version in the future, you’ll have to change the value of JAVA_HOME and point it to the correct executable path.
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I hope this tutorial not only helped you to set Java Home, it also taught you how you are doing it.
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If you are still facing issues or have any questions or suggestions, please let me know in the comments.
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--------------------------------------------------------------------------------
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via: https://itsfoss.com/set-java-home-ubuntu/
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作者：[Abhishek Prakash][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://itsfoss.com/author/abhishek/
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[b]: https://github.com/lujun9972
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[1]: https://itsfoss.com/run-java-program-ubuntu/
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[2]: https://maven.apache.org/
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[3]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2021/09/check-java-compiler-ubuntu.png?resize=750%2C310&ssl=1
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[4]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2021/09/java-compiler-check-ubuntu.png?resize=732%2C300&ssl=1
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[5]: https://itsfoss.com/install-java-ubuntu/
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[6]: https://linuxhandbook.com/which-command/
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[7]: https://linuxhandbook.com/symbolic-link-linux/
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[8]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2021/09/get-java-home-path-ubuntu.png?resize=800%2C283&ssl=1
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[9]: https://itsfoss.com/copy-paste-linux-terminal/
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[10]: https://i1.wp.com/itsfoss.com/wp-content/uploads/2021/09/setting-java-home-ubuntu.png?resize=800%2C268&ssl=1
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[11]: https://itsfoss.com/nano-editor-guide/
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[12]: https://linuxhandbook.com/echo-command/
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[13]: https://linuxhandbook.com/tail-command/
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[14]: https://i2.wp.com/itsfoss.com/wp-content/uploads/2021/09/set-java-home-bashrc-ubuntu.png?resize=786%2C348&ssl=1
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