java - 运行 import javax.swing.JOptionpane 时出错

Question

我对 Java 编程相对较新，我的代码出现输出错误，因为它与 swing 方面相关

import java.io.*;
import Java.text.DecimalFormat;


public class CurrencyConverter
{
public static void main(string[]args)throws IOException
{
String USDollar;
double USD, Euro, Pounds, Rouble;

BufferedReader dataIn=new BufferedReader (newInputStreamReader(System.in));

System.out.println();
System.out.println("\t\t CURRENCY CONVERTER");
System.out.println("\t\t Please enter the Dollar amount in US DOLLAR");
USDollar=dataIn.readLine();
USD=Double.parseDouble(USDollar);

Rouble=(USD*34.89);
Pounds=(USD*0.61);
      Euro=(USD*0.73);

System.out.println();
System.out.println("\t\tYour given amount $"+USD);
System.out.println("\t\tPounds $"+ Pounds);
System.out.println("\t\tRussian Rouble $"+ Rouble);
System.out.println("\t\tEuro $"+Euro);

}
}

import javax.swing.JOptionPane;

public class CSwing
{
public static void main(String[]args)
{
String USDollar;
double USD,Pounds,Rouble,Euros;

System.out.println("t\tCURRENCY CONVERTER");

USD = JOptionPane.showInputDialog(null,"Please enter the Dollar amount in USD");
dUSD=Double.parseDouble(USD);

Rouble=(USD*34.89);
Pounds=(USD*0.61);
Euro=(USD*0.73);

JOptionPane.showMessageDialog(null, "Your Given Amount: $" +(dUSD)
+"\n\nYour Rouble Conversion is:$"+(Rouble)
+"\n\nYour Pound Conversion is:$"+(Pound)
+"\n\nYour Euro Conversion is:$"+(Euro));
System.exit(0);
}
}  

工具输出错误:预期类、接口(interface)、枚举:导入javax.swing.JOptionpane:我用谷歌搜索了这个问题，试图自己解决这个问题，但我陷入了困境。我已经解决了所有其他存在的错误，这是唯一剩下的错误，但为什么我在解决这个错误时遇到了困难。我们将非常感谢您对此的帮助。

Answer 1

在这一行中:dUSD=Double.parseDouble(USD);您正在尝试从USD解析一个Double，它已经是一个双倍的。

Double.parseDouble(String S) 需要向其中传递一个 String 参数。不是Double。

快速修复:

import javax.swing.JOptionPane;

public class CSwing {
    public static void main(String[] args) {
        String usd;
        double dUSD, pounds, rouble, euros;

        System.out.println("t\tCURRENCY CONVERTER");

        usd  = JOptionPane.showInputDialog(null,
                "Please enter the Dollar amount in USD");
        dUSD = Double.parseDouble(usd);

        rouble = (dUSD * 34.89);
        pounds = (dUSD * 0.61);
        euros  = (dUSD * 0.73);

        JOptionPane.showMessageDialog(null, "Your Given Amount: $" + (dUSD)
                + "\n\nYour Rouble Conversion is:$ " + (rouble)
                + "\n\nYour Pound Conversion is:$ "  + (pounds)
                + "\n\nYour Euro Conversion is:$ "   + (euros));
        System.exit(0);
    }
}

至于您的CurrencyConverter，一切看起来都很好，只是有一些小的打印错误。

修复:

import java.io.*;

public class CurrencyConverter {
    public static void main(String[] args) throws IOException {
        String usDollar;
        double usd, euro, pounds, rouble;

        BufferedReader dataIn = new BufferedReader(new InputStreamReader(System.in));

        System.out.println();
        System.out.println("\t\t CURRENCY CONVERTER");
        System.out.println("\t\t Please enter the Dollar amount in US DOLLAR");
        usDollar = dataIn.readLine();
        usd      = Double.parseDouble(usDollar);

        rouble = (usd * 34.89);
        pounds = (usd * 0.61);
        euro   = (usd * 0.73);

        System.out.println();
        System.out.println("\t\tYour given amount $" + usd);
        System.out.println("\t\tPounds $" + pounds);
        System.out.println("\t\tRussian Rouble $" + rouble);
        System.out.println("\t\tEuro $" + euro);

    }
}