有人可以告诉我我的 Java 代码有什么问题吗？

Question

我正在尝试制作美元 <-> 日元转换器。如果您觉得这些数字不对，请相信我——我算了算。另外，我知道间距不对，但这并不重要。如果需要，可以在 N++ 中对其进行变形。

import java.util.Scanner;
import java.lang.Math;

public class jpy_usd {
public static void main(String[] args) {
    //Initializing variables and the scanner
    boolean isSourceUSD;
    double usd;
    double usdMult = 0.00803568;
    int jpy;
    double jpyMult = 124.449;
    Scanner scanner = new Scanner(System.in);

    //Selecting an input currency and checking for valid input arguments
    System.out.println("Choose your input currency. Type \'USD\' for U.S. Dollars or \'JPY\' for Japanese Yen.");
    while(isSourceUSD != true && isSourceUSD != false) {
        if(scanner.nextLine == "USD") {
            isSourceUSD = true;
        } else if(scanner.nextLine == "JPY") {
            isSourceUSD = false;
        } else {
            System.out.println("Invalid argument. Please use \'USD\' for U.S. Dollars or \'JPY\' for Japanese Yen.");
        }
    }

    //Asking for the input in the chosen currency and converting
    if(isSourceUSD) {
        System.out.println("Please enter the value to convert");
        usd = scanner.nextDouble;
        System.out.println(usd " in JPY is " (Math.round(usd * jpyMult)));
    } else if(!isSourceUSD) {
        System.out.println("Please enter the value to convert");
        jpy = scanner.nextInt;
        System.out.println(jpy " in USD is " (Math.round(jpy * usdMult)));
        }
    }
}

如果您想让我添加错误消息，我想我可以。没有太多解释，有 6 个错误平均分布在这两行中：

System.out.println(usd " in JPY is " (Math.round(usd * jpyMult)));
System.out.println(jpy " in USD is " (Math.round(jpy * usdMult)));

每个错误有两个 - 每行一个 - 所以行中的相似之处必须是相同的问题（呃）。那么，有人有任何线索吗？

P.S.: 如果代码除此之外还有任何问题，请务必指出。

P.S。 2：我知道我基本上是通过将每个字符放入此文本块来编写此代码 public，但请不要窃取。我知道有人要这样做，但请不要这样做。 ~奇迹

Answer 1

理想情况下，您的代码存在很多问题，首先是方法名称的命名约定、字符串比较。以下是使您的代码正常工作所需的最少代码更改：-

import java.util.Scanner;
import java.lang.Math;

public class jpy_usd {
public static void main(String[] args) {
    //Initializing variables and the scanner
    String isSourceUSD;
    double usd;
    double usdMult = 0.00803568;
    int jpy;
    double jpyMult = 124.449;
    Scanner scanner = new Scanner(System.in);

    //Selecting an input currency and checking for valid input arguments
    System.out.println("Choose your input currency. Type \'USD\' for U.S. Dollars or \'JPY\' for Japanese Yen.");

        if(scanner.nextLine() .equalsIgnoreCase( "USD")) {
            isSourceUSD = "USD";
        } else if(scanner.nextLine() .equalsIgnoreCase( "JPY")) {
            isSourceUSD ="JPY" ;
        } else {
            isSourceUSD="NA";
            System.out.println("Invalid argument. Please use \'USD\' for U.S. Dollars or \'JPY\' for Japanese Yen.");
        }

    //Asking for the input in the chosen currency and converting
    if(isSourceUSD.equalsIgnoreCase("USD")) {
        System.out.println("Please enter the value to convert");
        usd = scanner.nextDouble();
        System.out.println(usd +" in JPY is "+ (Math.round(usd * jpyMult)));
    } else if(isSourceUSD.equalsIgnoreCase("JPY")) {
        System.out.println("Please enter the value to convert");
        jpy = scanner.nextInt();
        System.out.println(jpy+ " in USD is " +(Math.round(jpy * usdMult)));
        }
    else{
        System.out.println("Do nothing!!!");
    }
    scanner.close();
    }
}

有人可以告诉我我的 Java 代码有什么问题吗？

Could someone please tell me what's wrong with my Java code?

java

currency

converter