How do I add functioning operations $"+,-,*,/"$ in this Java code? I've got the program to accept and display two variables $($numA$,$ numB$)$ but now I need to implement code so when the user types an operator, it manipulates the two values and displays the result.

import java.util.Scanner;

public class App $\{$

public static void main$($String$[]$ args$)\{$

Scanner scan $=$ new Scanner$($System$.$in$)$;

Character command $=\text{'}\_\text{'}$;

$//$ loop until user quits

while $($command $!=\text{'}$q$\text{'})\{$

printMenu$()$;

System.out.print$("$Enter a command: $")$;

command $=$ menuGetCommand$($scan$)$;

executeCommand$($scan$,$ command$)$;

if $($command $==\text{'}$a$\text{'})\{$

System.out.println$("$Enter a number: $")$;

double numA $=$ scan.nextDouble$()$;

if $($numA $>0)\{$

System.out.printf$("$A $="+$ numA $+"$

$")$;

$\}$

$\}$

if $($command $==\text{'}$b$\text{'})\{$

System.out.println$("$Enter a number: $")$;

double numB $=$ scan.nextDouble$()$;

if $($numB $>0)\{$

System.out.printf$("$B $="+$ numB $+"$

$")$;

$\}$

$\}$

$\}$

scan.close$()$;

$\}$

$//$

$//$ menu functions

$//$

private static void printMenuLine$()\{$

System.out.println$($

$"----------------------------------------------------------"$

$)$;

$\}$

private static void printMenuCommand$($Character command, String desc$)\{$

System.out.printf$("\%$s$\backslash$t$\%$s

$",$ command, desc$)$;

$\}$

$//$ prints the menu

public static void printMenu$()\{$

printMenuLine$()$;

System.out.println$("$ChavviCalc$")$;

printMenuLine$()$;

printMenuCommand$(\text{'}$a$\text{'},$ "Enter a value for A$")$;

printMenuCommand$(\text{'}$b$\text{'},$ "Enter a value for B$")$;

printMenuCommand$(\text{'}+\text{'},$ "Add"$)$;

printMenuCommand$(\text{'}-\text{'},$ "Subtract"$)$;

printMenuCommand$(\text{'}*\text{'},$ "Multiply"$)$;

printMenuCommand$(\text{'}/\text{'},$ "Divide"$)$;

printMenuCommand$(\text{'}$c$\text{'},$ "Clear"$)$;

printMenuCommand$(\text{'}$q$\text{'},$ "Quit"$)$;

printMenuLine$()$;

$\}$

$//$ get first character from input

private static Character menuGetCommand$($Scanner scan$)\{$

Character command $=\text{'}\_\text{'}$;

String rawInput $=$ scan.nextLine$()$;

if $($rawInput$.$length$()>0)\{$

rawInput $=$ rawInput.toLowerCase$()$;

command $=$ rawInput.charAt$(0)$;

$\}$

return command;

$\}$

$//$ calculator functions

private static Boolean executeCommand$($Scanner scan, Character command$)\{$

Boolean success $=$ true;

switch $($command$)\{$

case $\text{'}$q$\text{'}$:

System.out.println$("$Thank you for using Chavvi Calc"$)$;

break;

case $\text{'}$a$\text{'},\text{'}$b$\text{'}$:

break;

default:

System.out.println$("$ERROR: Unknown commmand"$)$;

success $=$ false;

$\}$

return success;

$\}$

$\}$