Working with multiple versions

Most of the times we as developers are working on multiple version of the language or the framework. If not managed properly it can be a nightmare dealing with different projects which use different versions of the same language. Say, project A uses python2 and project B uses python3. In python we have virtual environments which can be managed using, among many others, pipenv. Likewise for Ruby we have rbenv.

There are quite a few languages that run on JVM(Java Virtual Machine). Java, Groovy, Scala being the most prominent ones. SDKMAN! is a tool that facilitates maintaining different versions of JVM based languages.

Installing SDKMAN

curl -s "https://get.sdkman.io" | bash
source "$HOME/.sdkman/bin/sdkman-init.sh" #activating initialization shell script

After Installation we can see the list of all the supported languages and versions using:

sdk list

Likewise to view versions of a particular sdk we can use:

sdk list java

Replace java with another sdk such as groovy, scala, ant for related information. As always you can explore options by issuing sdk --help

All of the installations are stored inside $SDKMAN_DIR/candidates from where we can select the default version sdk default $language $version or even select one for just the current terminal session sdk use $language $version.

Now that we have a very easy package manager for JVM languages lets go about installing java-9 so that we can use Jshell which is the REPL (Read, evaluate, print, repeat) feature to interact with JVM. No need to write a beautiful class with main object just so you can experiment with some esoteric String method.

Finding what java versions are supported

sdk list java

================================================================================
Available Java Versions
================================================================================
 > * 9.0.7-zulu                                                                    
     9.0.4-openjdk                                                                 
     8.0.172-zulu                                                                  
     8.0.171-oracle                                                                
     7.0.181-zulu                                                                  
     6.0.107-zulu                                                                  
     10.0.1-zulu                                                                   
     10.0.1-oracle                                                                 
     10.0.0-openjdk                                                                
     1.0.0-rc1-graal                                                               
                                                                                   
                                                                                   
                                                                                   
                                                                                   
                                                                                   

================================================================================
+ - local version
* - installed
> - currently in use

For our example let’s install zulu java-9.

sdk install java 9.0.7-zulu

If you don’t want to mess around with your system, don’t make it as the default one yet. Now java-9 can be found under ~/.sdkman/candidates/java. Jshell resides inside bin directory along with other java programs like java javac javadoc.

Make it executable by issuing: sudo chmod +x jshell

For ease of use we can create a symlink to this executable so that we can invoke it from anywhere in the system.

sudo ln -s ~/.sdkman/candidates/java/9.0.7-zulu/bin/jshell  /usr/local/bin/jshell

Now we are ready to launch jshell and explore all the REPL beauty that it brings along.

jshell

You can now get your hands dirty