Please write this Java program as simple as possible and use comments throughout to explain what is happening. Thank you!

4.15 (Phone key pads) The international standard letterumber mapping found on the telephone is shown below Write a program that prompts the user to enter a letter and displays its correspond- ing number Enter a letter: A The corresponding number is 2 Enter a letter: a The corresponding number is 2 Enter a letter: + + is an invalid input