Solution: Building Java Applications

To compile this Java code into class files, you can use the command:

javac UserValidatorExample.java

Once you have created all the class files, you can package them using the jar command with the statement:

jar -cfe validator.jar UserValidatorExample *.class

This statement uses the -c flag to create a new jar, the -f flag to specify the filename validator.jar and the -e flag to provide the class to use as an entry point, UserValidatorExample. It creates the jar using all the files in the current directory with the class extension.

Finally, you can run the jar using the command:

java -jar validator.jar

You should see the output of the main class running, which is:

false
true
true
false
`