Java中的菜单字符

我是Java编程的新手，在理解如何接受用户输入并将其转换为程序能够理解的内容方面一直存在问题。我试图在这个程序中输入用户的字符，并让程序接受它并在switch语句中使用它。请有人告诉我，我会用什么关键词或技术来输入一个字符，或者把一个字符串翻译成我的程序中的字符，而不会让它变得非常复杂？我感谢你的帮助，并提前感谢你！

import java.util.Scanner;
//import java.util.Scanner;
public class VendingMachine;
{
   public static void main(String[] args)
   {
      Scanner scanner = new Scanner (System.in);
      int selection=0;
      int x=0;
      float origItemNum = 15;
      float origDebitBal = 15;
      double balanceDebit;
      double balanceItemNum;
      double items = 0;
      char choice = 0;
      //initialize variables

      boolean validSelection;
      System.out.print("nInitial Account Settings:");
      System.out.print("nUnused Item Capacity: 15");
      System.out.print("nCost (so far) this month: $15");
      balanceDebit=origDebitBal;
      balanceItemNum = origItemNum;
      while(x==0)
      {
         System.out.print("nMenu:"); 
         System.out.print("nB (show Bill and starts new month)");  
         System.out.print("nU (show Unused capacity for the current month)"); 
         System.out.print("nC (Consume vending items now -- " +
               "purchase candy bar, bag of chips, etc.)"); 
         System.out.print("nA (buy Additional items for current month)"); 
         System.out.print("nQ (show bill and Quit)"); 
         String strUserAnswer;
         String strQuestion;
         String choiceVerify;
         Scanner input_stream = new Scanner(System.in);
         strQuestion = new String("What choice would you like? Please" +
               "enter in either option A, B, U, C- or enter E to quit. ");
         strUserAnswer = input_stream.nextLine();
         choice = (char) Integer.parseInt(strUserAnswer);
         choiceVerify = ("You chose choice: ");
         System.out.print(strUserAnswer);
         input_stream.close();
         switch (selection)
         {
         case 'b':
         case 'B': 
            System.out.print("nnClosing bill for month:");
         //   System.out.print("nUnused items (lost):" );
         //   System.out.print(balanceItemNum);
          //  System.out.print("nFinal amount due immediately: $" );
          //  System.out.print(balanceDebit);
           // System.out.print("nStarting new month ...Available items: 15");
           // balanceItemNum = 15;
           // balanceDebit = 15;
            break;
         case 'u':
         case 'U':
            System.out.print("nUnused capacity of items you can use: " );
           // System.out.print(balanceItemNum);
           // System.out.print("nYour debit balance: $" );
           // System.out.print(balanceDebit);
            break;
         case 'c':
         case 'C':
            System.out.print("nNumber of items you want to purchase:");
          //  Scanner input = new Scanner(System.in);
            //items = input.nextDouble();
            //balanceItemNum = balanceItemNum-items;
           // balanceDebit = balanceDebit - items;
           // System.out.print("nAvailable Items: " );
           // System.out.print(balanceItemNum);
            break;
         case 'a':
         case 'A': 
            String numberString = JOptionPane.showInputDialog("nAdditional " +
                  "items purchase in sets of 10 (1-3):");
           // double number = Double.parseDouble(numberString);
            //      while (number == 1 || number == 2 || number == 3)
           // number = number * 11;
           // balanceItemNum = balanceItemNum + number;
           // balanceDebit = balanceDebit + number;
            break;
         case 'e':
         case 'E':
            System.out.print("nYour debit balance: $" );
           // System.out.print(balanceDebit);
            break;
         }
      }
      while (choice != 'e' && choice != 'E');
      System.out.print("nError: Please enter in either B, U, C, A or Q.");
      return;
   }
}