Question

这是我的java类简介的基本货币转换器。我应该能够使用静态费率在日元，美元，英镑和欧元之间进行转换。它有效，但我很想知道我是否以最有效的方式做到了。它似乎很长，看起来像一个巨大的混乱。只是想要一些反馈。

import java.util.Scanner;

public class currency
{

     public currency()
    {
        char us_dollar_sym = 36;
        char pound_sym = 163;
        char yen_sym = 165;
        char euro_sym = 8364; 

        String us_dollar = "Dollars"; 
        String pound = "Pounds";
        String yen = "Yen";
        String euro = "Euros";
        double rate = 0;


        // Interface
        System.out.println("Welcome to the Currency Converter Program \n");
        System.out.println("Use the following codes to input your currency choices: \n 1 - US dollars \n 2 - Euros \n 3 - British Pounds \n 4 - Japanese Yen \n");

        // 
        System.out.println("Please choose the input currency:");
        Scanner in = new Scanner(System.in);
        int choice = in.nextInt(); 

       String inType = null;
        switch(choice) {
        case 1: inType = "US Dollars >> " + us_dollar_sym;  break;
        case 2: inType = "Euros >> " + euro_sym; break;
        case 3: inType = "British Pounds >> " + pound_sym; break;
        case 4: inType = "Japanese Yen >> " + yen_sym; break;
        default:
        System.out.println("Please restart the program & enter a number from the list.");
        return;
      }

        System.out.println("Please choose the output currency");
        int output = in.nextInt();

        System.out.printf("Now enter the input in " + inType);
        double input = in.nextDouble(); 

      if (choice == output) 
        System.out.println("Same currency no need to convert");

      if (choice == 1 && output == 2)
        { 
           double dollar_euro_rate = 0.78391;
           rate = input * dollar_euro_rate;
           System.out.printf( "%s" + input + " at a conversion rate of " + dollar_euro_rate + " Dollars to %s = %.2f\n", (char)us_dollar_sym, euro, rate);
        }
        else if (choice == 1 && output == 3){ 
           double dollar_pound_rate = 0.621484;
           rate = input * dollar_pound_rate;
           System.out.printf( "%s" + input + " at a conversion rate of " + dollar_pound_rate + " Dollars to %s = %.2f\n", (char)us_dollar_sym, pound, rate);
        }
        else if (choice == 1 && output == 4){ 
          double dollar_yen_rate = 107.174;
          rate = input * dollar_yen_rate;
          System.out.printf( "%s" + input + " at a conversion rate of " + dollar_yen_rate + " Dollars to %s = %.2f\n", (char)us_dollar_sym, yen, rate);
        }
      if (choice == 2 && output == 1)
      {
          double euro_dollar_rate = 1.27579;
          rate = input * euro_dollar_rate;
          System.out.printf( "%s" + input + " at a conversion rate of " + euro_dollar_rate + " Euros to %s = %.2f\n", (char)euro_sym, us_dollar, rate);
        }
        else if (choice == 2 && output == 3)
        {
          double euro_pound_rate = 0.792648;
          rate = input * euro_pound_rate;
          System.out.printf( "%s" + input + " at a conversion rate of " + euro_pound_rate + " Euros to %s = %.2f\n", (char)euro_sym, pound, rate);
        }
        else if (choice == 2 && output == 4)
        {
          double euro_yen_rate = 136.708;
          rate = input * euro_yen_rate;
          System.out.printf( "%s" + input + " at a conversion rate of " + euro_yen_rate + " Euros to %s = %.2f\n", (char)euro_sym, yen, rate);
        }
      if (choice == 3 && output == 1)
      {
          double pound_dollar_rate = 1.60972;
          System.out.printf( "%s" + input + " at a conversion rate of " + pound_dollar_rate + " Pounds to %s = %.2f\n", (char)pound_sym, us_dollar, rate);
        }
        else if (choice == 3 && output == 2)
        {
          double pound_euro_rate = 1.26161;
          System.out.printf( "%s" + input + " at a conversion rate of " + pound_euro_rate + " Pounds to %s = %.2f\n", (char)pound_sym, euro, rate);
        }
        else if (choice == 3 && output == 4)
        {
          double pound_yen_rate = 172.511;
          System.out.printf( "%s" + input + " at a conversion rate of " + pound_yen_rate + " Pounds to %s = %.2f\n", (char)pound_sym, yen, rate);
        }
      if (choice == 4 && output == 1)
      { 
          double yen_dollar_rate = 0.00932574;
          System.out.printf( "%s" + input + " at a conversion rate of " + yen_dollar_rate + " Yen to %s = %.2f\n", (char)yen_sym, us_dollar, rate);
        }
        else if (choice == 4 && output == 2)
        { 
          double yen_euro_rate = 0.00730615;
          System.out.printf( "%s" + input + " at a conversion rate of " + yen_euro_rate + " Yen to %s = %.2f\n", (char)yen_sym, euro, rate);
        }
        else if (choice == 4 && output == 3)
        {
          double yen_pound_rate = 0.00579135;
          System.out.printf( "%s" + input + " at a conversion rate of " + yen_pound_rate + " Yen to %s = %.2f\n", (char)yen_sym, pound, rate);
        }
       System.out.println("Thank you for using the currency converter");
    }
}

Answer 1

我总是小心使用整数输入。如果有人键入char，您的程序可能会崩溃，因为会发生异常。接受该号码的字符可能是更安全的替代方案。

检查＆＃34;选择＆＃34;和＆＃34;输出＆＃34;在同一个if语句中，它需要更多资源。嵌套if语句可能会提高效率。这将使用if语句进行选择，并在其中输出if语句。

Answer 2

由于您将货币称为int，我将使用n×m矩阵来存储汇率。 n将是第一种货币而m是第二种货币。使用两个int，您可以追溯正确的汇率。

矩阵中的对角线为1（因为USD＆gt;＆gt; USD = 1）。

最后，写一个函数来计算汇率并返回相应的文本（你可以使用一个hashmap，int作为键，名称（string）作为值）

exchange_rate = currency[1][2];


HashMap hm = new HashMap();

hm.put(1, new string("USD");

等...

Answer 3

将所有费率表示为一个标准值的乘数，例如使用美元作为标准值。那么英镑的转换价值将是1.60，美元将是1.0，欧元将是1.29。然后转换计算将是：

从价值*从转换* 1 /转换

例如从1英镑到欧元将是：

1 * 1.60 *（1 / 1.29）= 1.24

如果将所有费率存储在HashMap中，则可以完全避免使用switch语句。

Answer 4

为什么您使用这种方式转换货币。你有 JSR 354货币和货币API 这里有一些你可以使用的例子，它真的很容易使用和快速：

Traceback (most recent call last):  
  File "D:/Acads/7.1 Sem/BTP/FaceDetect-master/6.py", line 28, in <module>  
    eyes = eyeCascade.detectMultiScale(roi)  
NameError: name 'roi' is not defined

基本货币转换器 - 寻找反馈

4 个答案: