Simple Java calculator with two operands
Your code

Simple is nice. But it would have been good to decompose your solution to multiple methods, for example at least:


a method to read a double
a method to perform the calculation: take the numbers and an operator as parameter and return the result


Other issues:


Don't pre-calculate the result of all possible calculations when you will only use one of them
The print statements are repetitive. If you decomposed the solution to multiple methods, naturally you would have factored out duplicated elements.
Naming, as @Caridorc already covered.


The instructor's code

Sort of nicely written, decomposed, but this is bad code:


Delaying the validation of input by carrying around the String values of supposed numeric values is a terrible idea. As @Caridorc said it too, the numeric input should have been read into the desired types (double in this example) and lift the burden of uncertainty from the rest of the code.
The getInput method is a good idea, but poorly executed. Creating a new Scanner for every piece of input is a waste. Just like there is one System.in, a single Scanner could be used and passed to the method. The method is a huge missed opportunity for actually validating the input, and returning the desired type, instead of a String.
Large try blocks are also better to avoid, and the large try block in the middle is just another consequence of delaying the input validation, that could have been done much better earlier.