Update UserInterface.java

-Removed the 2 Scanner's and made 1 global scanner where the scope is the whole class rather than every separate method

-Changed the while (userChoice != 1 && userChoice != 2 && userChoice != 3 && userChoice != 4 && userChoice !=5) to while (userChoice < 1 || userChoice > 5) in the firstMenu() method.

-Changed the if-statements in firstMenuRedirection() method to a switch statement.

-Changed method names to comply with naming conventions

-Moved the while loop in firstMenu() to encompass the try-catch block

-Removed UserInterface UI = new UserInterface() b/c this is the UserInterface