Command for inequality of char
There are some minor issues with this:


The condition to check the value of choice is duplicated
The program will crash if the input is empty
The variable choice is declared outside the loop body
The formatting is a bit unusual


I suggest this way instead:

while (true) {
    System.out.println("Would you like to continue?(y/n)");
    String line = sc.nextLine();
    if (!line.isEmpty()) {
        char choice = line.charAt(0);
        if (choice == 'y' || choice == 'n') {  
            return choice;
        }
    }
    System.out.println("Invalid Entry");
}