# INSTALL AND MANAGE MULTIPLE JAVA JDK AND JRE VERSIONS ON UBUNTU **INSTALL AND MANAGE MULTIPLE JAVA JDK AND JRE VERSIONS ON UBUNTU** **Step 1. Check Java JDK version** Open a terminal and check java JDK version: ```plaintext $ javac -version ``` If you do not have a Java JDK installed the terminal response will look like: ```plaintext Command 'javac' not found, but can be installed with: sudo apt install default-jdk # version 2:1.11-72, or sudo apt install openjdk-11-jdk-headless # version 11.0.8+10-0ubuntu1~20.04 sudo apt install openjdk-13-jdk-headless # version 13.0.4+8-1~20.04 sudo apt install openjdk-14-jdk-headless # version 14.0.2+12-1~20.04 sudo apt install openjdk-8-jdk-headless # version 8u265-b01-0ubuntu2~20.04 sudo apt install ecj # version 3.16.0-1 ``` As you can see, the terminal response displays the commands to install various headless JDK versions. **Step 2. Install Java JRE/JDKs** **1. Install Java 11 JRE/JDK** At the time of writing, Java 11 is the latest long-term supported (LTS) version of Java. It is the default Java development and runtime version. Installing a JDK package will also install the corresponding JRE. Install Java 11 JDK: ```plaintext $ sudo apt install default-jdk ``` Check JRE version: ```plaintext $ java -version ``` The response will look like: ```plaintext openjdk version "11.0.9" 2020-10-20 OpenJDK Runtime Environment (build 11.0.9+11-Ubuntu-0ubuntu1.20.04) OpenJDK 64-Bit Server VM (build 11.0.9+11-Ubuntu-0ubuntu1.20.04, mixed mode, sharing) ``` Check JDK version: ```plaintext $ javac -version ``` The response will look like: ```plaintext javac 11.0.9 ``` **2. Install Java 8 JRE/JDK** Install Java 8 JDK: ```plaintext $ sudo apt install openjdk-8-jdk ``` If you check current JDK and JRE versions it will still display Java 11. **3. Install Java 13 JRE/JDK** Install Java 13 JDK: ```plaintext $ sudo apt install openjdk-13-jdk ``` Check current JRE version: ```plaintext $ java -version ``` The response will look like: ```plaintext openjdk version "13.0.4" 2020-07-14 OpenJDK Runtime Environment (build 13.0.4+8-Ubuntu-120.04) OpenJDK 64-Bit Server VM (build 13.0.4+8-Ubuntu-120.04, mixed mode) ``` Check current JDK version: ```plaintext $ javac -version ``` The response will look like: ```plaintext javac 13.0.4 ``` As you can see the current JRE and JDK are version 13. **4. Install Java 14 JRE/JDK** Install Java 14 JDK: ```plaintext $ sudo apt install openjdk-14-jdk ``` Check current JRE: ```plaintext $ java -version ``` The response will look like: ```plaintext openjdk version "14.0.2" 2020-07-14 OpenJDK Runtime Environment (build 14.0.2+12-Ubuntu-120.04) OpenJDK 64-Bit Server VM (build 14.0.2+12-Ubuntu-120.04, mixed mode, sharing) ``` Check current JDK: ```plaintext $ javac -version ``` The response will look like: ```plaintext javac 14.0.2 ``` Again, we can see the current JRE and JDK are version 14. **Step 2. Manage Installed Java JRE/JDKs** Now that we have installed multiple Java JRE/JDK versions we can switch between them. **1. Switch JRE version** Check installed JREs: ```plaintext $ sudo update-alternatives --config java ``` The response will look like: ```plaintext There are 4 choices for the alternative java (providing /usr/bin/java). Selection Path Priority Status ------------------------------------------------------------ * 0 /usr/lib/jvm/java-14-openjdk-amd64/bin/java 1411 auto mode 1 /usr/lib/jvm/java-11-openjdk-amd64/bin/java 1111 manual mode 2 /usr/lib/jvm/java-13-openjdk-amd64/bin/java 1311 manual mode 3 /usr/lib/jvm/java-14-openjdk-amd64/bin/java 1411 manual mode 4 /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java 1081 manual mode Press to keep the current choice[*], or type selection number: ``` Now you can switch to another JRE or keep the current version. **2. Switch JDK version** Check installed JDKs: ```plaintext $ sudo update-alternatives --config javac ``` The response will look like: ```plaintext There are 4 choices for the alternative javac (providing /usr/bin/javac). Selection Path Priority Status ------------------------------------------------------------ * 0 /usr/lib/jvm/java-14-openjdk-amd64/bin/javac 1411 auto mode 1 /usr/lib/jvm/java-11-openjdk-amd64/bin/javac 1111 manual mode 2 /usr/lib/jvm/java-13-openjdk-amd64/bin/javac 1311 manual mode 3 /usr/lib/jvm/java-14-openjdk-amd64/bin/javac 1411 manual mode 4 /usr/lib/jvm/java-8-openjdk-amd64/bin/javac 1081 manual mode Press to keep the current choice[*], or type selection number: ``` Again, you can now switch to another JDK or keep the current version. **Step 3. Add JAVA\_HOME environment variable** Java applications may use environment variables. JAVA\_HOME is a common one so we will now we add this. Edit /etc/environment file: ```plaintext $ sudo nano /etc/environment ``` Add the following line to the file and save: ```plaintext JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64/bin/" ``` In the above example we are using Java 11. To apply the changes you will need to log out then log in again. To apply the changes in your current terminal session use the source command: ```plaintext $ source /etc/environment ``` Check the environment variable was set: ```plaintext $ echo $JAVA_HOME ``` The response should look like: ```plaintext sr/lib/jvm/java-11-openjdk-amd64/bin/ ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://blog.micsoftvn.com/use-cases/for-sysadmin/install-and-manage-multiple-java-jdk-and-jre-versions-on-ubuntu.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. 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