Java programming problem, could you please add comments "//" so that I know why you took the steps you did? Thank you!

Write a program that prompts the user to input a 4 digit integer - Assume the input will always be exactly 4 digits. Output the integer with the digits in reverse. Write your program so that it requires the use of only two variables total. Use your program to verify the following: Execution 1: Input: 6578 Output: 8765 Execution 2: Input: 1234 Output: 4321 Execution 3: Input: 1005 Output: 5001