For a long time, there has been no standard shell shipped with the Java programming language to experiment with new language features or libraries or for rapid prototyping. If you wanted to do this, you could write a test application with a main method, compile it with javac, and run it. This could be done either at the command line or using a Java IDE; however, in both cases, this is not as convenient as having an interactive shell for the purpose.
Starting an interactive shell in JDK 9 is as simple as running the following command (assuming the bin directory of your JDK 9 installation is in the current path):
jshell
You may find it somewhat puzzling that an interactive shell has not been introduced earlier ...
