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Sorry, I have no idea how to use your IDE.
Once the program is finished being developed, move it out of the IDE to execute it.

That is the command line that should be used when the program is executed.
How do you execute the program?
Here's a sample of the console when I execute the java command:
...

The user needs to enter:
java Power 2
to execute the program without any errors.

If you want the program to catch errors
Pseudo code:
if length of the array passed to main() is < 1
then print...

The error message says that the array: args is empty (it does not have an element at index 0)
The code should test the length of the args array and make sure it has some content before trying to get...

Please copy the full text of the error message and paste it here.