java - Java ATM 项目中使用 If 语句进行切换

Question

现在我正在开发一个 ATM 项目。用户将输入姓名、余额、交易类型和交易金额。交易类型为提款(W)、存款(D)和R(报告)，我使用的是switch，有 3 个案例 W、D、R。如果您出现以下情况，程序将输出错误: 输入错误的代码、您没有足够的资金来执行您选择的交易类型、以及您输入的金额为负数。现在，我在尝试设置开关时遇到了困难。我的代码如下，任何帮助将不胜感激!谢谢

import java.io.*;
import java.util.*;
public class atmValidator {

   public static void main(String[] args) {

      String fname = " ", lname = " ";

      double balbefore = 0.0, balafter = 0.0, transamount = 0.0;

      char code = ' ';

      Scanner screen = null;
      FileInputStream fis = null;
      FileOutputStream fos = null;
      PrintWriter pw = null;

      //Declaring the variables/scanner/etc.

      try {
        fis = new FileInputStream ("transactions.txt");
        fos = new FileOutputStream ("statement.txt");

        screen = new Scanner (fis);
        pw = new PrintWriter (fos);

      } catch (FileNotFoundException e) {
          System.out.println("File not found");
          System.exit(0);
      }

      //The try/catch for reading from the file

      while (screen.hasNext()) {
        fname = screen.next();
        lname = screen.next();
        balbefore = screen.nextDouble();
        code = screen.next().charAt(0);
        transamount = screen.nextInt();

      //A while loop to gather the info from the file, and the variables getting their values from the files.

        switch (code) {

            case 'D':
                balafter = balbefore + transamount;
                if (transamount <0) {
                    pw.println("ERROR: Enter positive amount.");
                }
                else if (balafter < 300) {
                    pw.println("Warning, balance below $300");
                }

                {

                   // Where I am stuck at :(   
                }
          }
       }        
       screen.close();
       pw.close();

    }   
}
//Sorry for the weird braces and spaces

Answer 1

您可以在 switch 主体中编写如下情况。您可以进一步延长条件，但在这里我只是给您举了一个示例。如果字符不是D、W或R，则执行default case。

    switch (code) {
        case 'D':
            balafter = balbefore + transamount;
            System.out.println("");
            if (balafter < 0) {
                pw.println("Insufficent funds");

            } else if (balafter < 300) {
                pw.println("Warning, balance below $300");
            }else{
                pw.println("Well. You have now " + balafter + "$");
            }
            break;
        case 'W':
            balafter = balbefore - transamount;
            if (transamount > balbefore) {
                pw.println("Sorry. You don't enough funds.");

            } else if (transamount <= balbefore && balafter < 300) {
                pw.println("Warning, balance below $300");
            } else {
                pw.println("The withdrawl was successful.");
            }
            break;
        case 'R':
            balafter = balbefore + transamount;
            if (balafter < 0) {
                pw.println("Insufficent funds");

            } else if (balafter < 300) {
                pw.println("Warning, balance below $300");
            } else {
                pw.println("Good. Your balance is " + balAfter);
            }
            break;
        default:
            System.out.println("Nothing to do.");
            break;
    }