Challenges

Remember the rules for this are

• Try to use only the information given up to this point in this book.
• Try not to give up until you've given it a solid attempt

Challenge 1.

Make a program under src/CLI.java. The rest of these challenges will all be adding features to that program.

class CLI {
    // CODE HERE

    void main(String[] args) {
        // CODE HERE
    }
}

First, make it so that java src/CLI.java prints "No arguments provided" and immediately exits.

Challenge 2.

Make it so that java src/CLI.java 8 will print 64 and then exit. If you ran java src/CLI.java 5 it would print 25 and so on. For any number it should print it's square.

Challenge 3.

Make the operation to perform overridable. java src/CLI.java --operation square 8 should do the same thing as java src/CLI.java 8. java src/CLI.java --operation factorial 8 should print out 8 factorial (which is 40320) instead of 64.

Challenge 4.

If a -d argument is provided then, instead of printing the result, the program should write the result to a file at the specified path.

So java src/CLI.java -d out.txt 9 should write 81 into a file named out.txt. The order that -d and --operation are provided should not matter. java src/CLI.java -d out.txt --operation factorial 3 and java src/CLI.java --operation factorial -d out.txt 3 should behave exactly the same.

Challenge 5.

Make java src/CLI.java --help print out a help message describing the different flags you can provide and their meanings. To see what this should look somewhat like first run java --help.