You can choose from a long list of Java versions and distributions if you use the 64-bit version of the Raspberry Pi Operating System. But this 64-bit OS is only available for Raspberry Pi board versions with an ARMv7 or ARMv8 processor.
You can check the installed Java version in the terminal. On a board with ARMv7 or ARMv8, with a correctly installed JDK, you will get this result:
$ java -version
openjdk version "11.0.3" 2019-04-16
OpenJDK Runtime Environment (build 11.0.3+7-post-Raspbian-5)
OpenJDK Server VM (build 11.0.3+7-post-Raspbian-5, mixed mode)
On an ARMv6 version, you will get an error:
$ java -version
Error occurred during initialization of VM
Server VM is only supported on ARMv7+ VFP
If you are not sure which type of board you have, you can check this in the terminal with cat /proc/cpuinfo, for instance for a Raspberry Pi B+ 1.2:
$ cat /proc/cpuinfo
processor : 0
model name : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS : 697.95
Features : half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part : 0xb76
CPU revision : 7
Hardware : BCM2835
Revision : 0010
Serial : 000000005f9ba615
Model : Raspberry Pi Model B Plus Rev 1.2
The sources for Java are available as open-source on OpenJDK, which means, if you can’t find the correct version for a specific board, it is possible to compile it yourself. Luckily there are different suppliers providing ready-made packages of the JDK for multiple platforms. But only Azul seems to have one which is a perfect fit for Raspberry Pi’s with an ARMv6: the Zulu community edition of JDK 11.
To get started with Zulu JDK, download and uncompress it to your board:
$ cd /usr/lib/jvm
$ sudo wget https://cdn.azul.com/zulu-embedded/bin/zulu11.41.75-ca-jdk11.0.8-linux_aarch32hf.tar.gz
$ sudo tar -xzvf zulu11.41.75-ca-jdk11.0.8-linux_aarch32hf.tar.gz
$ sudo rm zulu11.41.75-ca-jdk11.0.8-linux_aarch32hf.tar.gz
$ ls -l
total 12
lrwxrwxrwx 1 root root 21 Jul 23 15:58 java-1.11.0-openjdk-armhf -> java-11-openjdk-armhf
drwxr-xr-x 9 root root 4096 Aug 20 11:41 java-11-openjdk-armhf
drwxr-xr-x 2 root root 4096 Aug 20 11:41 openjdk-11
drwxrwxr-x 10 111 122 4096 Jul 10 16:50 zulu11.41.75-ca-jdk11.0.8-linux_aarch32hf
Now we have the JDK11 ready to be used, but it still needs to be configured, so the OS is aware of it.
$ sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/zulu11.41.75-ca-jdk11.0.8-linux_aarch32hf/bin/java 1
$ sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/zulu11.41.75-ca-jdk11.0.8-linux_aarch32hf/bin/javac 1
At this moment we can select the new JDK to link it to the “java” and “javac” command.
$ sudo update-alternatives --config java
There are 2 choices for the alternative java (providing /usr/bin/java).
Selection Path Priority Status
------------------------------------------------------------
* 0 /usr/lib/jvm/java-11-openjdk-armhf/bin/java 1111 auto mode
1 /usr/lib/jvm/java-11-openjdk-armhf/bin/java 1111 manual mode
2 /usr/lib/jvm/zulu11.41.75-ca-jdk11.0.8-linux_aarch32hf/bin/java 1 manual mode
Press <enter> to keep the current choice[*], or type selection number: 2
update-alternatives: using /usr/lib/jvm/zulu11.41.75-ca-jdk11.0.8-linux_aarch32hf/bin/java to provide /usr/bin/java (java) in manual mode
$ sudo update-alternatives --config javac
There are 2 choices for the alternative javac (providing /usr/bin/javac).
Selection Path Priority Status
------------------------------------------------------------
* 0 /usr/lib/jvm/java-11-openjdk-armhf/bin/javac 1111 auto mode
1 /usr/lib/jvm/java-11-openjdk-armhf/bin/javac 1111 manual mode
2 /usr/lib/jvm/zulu11.41.75-ca-jdk11.0.8-linux_aarch32hf/bin/javac 1 manual mode
Press <enter> to keep the current choice[*], or type selection number: 2
update-alternatives: using /usr/lib/jvm/zulu11.41.75-ca-jdk11.0.8-linux_aarch32hf/bin/javac to provide /usr/bin/javac (javac) in manual mode
Now let’s check the Java version:
$ java -version
openjdk version "11.0.8" 2020-07-14 LTS
OpenJDK Runtime Environment Zulu11.41+75-CA (build 11.0.8+10-LTS)
OpenJDK Client VM Zulu11.41+75-CA (build 11.0.8+10-LTS, mixed mode)
OK, ready to run Java 11 applications on the Raspberry Pi with ARMv6!
If you want more info, or use JavaFX, check these blog posts: