Question

我一直收到错误＆＃34; String无法转换为double＆＃34;我已经尝试将我的变量重新定义为int但这似乎不起作用 - 我只是得到一个标志，说丢失会发生转换为double。我很好奇是否在使用错误的JOptionPane时要求用户输入或者我的变量声明是错误的。

非常感谢任何帮助。

package pf_javaass01c;
import javax.swing.JOptionPane;
public class ConversionCalculator 
{
    final static String HEADING = "Conversion Calculator";
    final static double CONVERSION = 0.6214;
    final static double PI = 3.14159;

    public static void main(String[] args) 
    {
        // Input Variables
        double kilometers, convertedKilometers, miles, convertedMiles;
        double width, length, areaRectangle, perimeterRectangle;
        double radius, circumference, areaCircle;

        // Kilometer to Miles Calculator
        kilometers = JOptionPane.showInputDialog(null, "Please enter a kilometer value you wish to convert to miles;", HEADING,     JOptionPane.QUESTION_MESSAGE);
        convertedKilometers = kilometers * CONVERSION;
        JOptionPane.showMessageDialog(null, kilometers + " kilometers is equal to " + convertedKilometers + " miles.", HEADING, JOptionPane.INFORMATION_MESSAGE);
         } // End of main

} // End of ConversionCalculator

Answer 1

JOptionPane返回的值为String。您正尝试将该值放入kilometers，double。你基本上试图将球体装入三角形孔中。结果，发生了错误。

解决方案是简单地解析，或将字符串转换为double。为此，请致电Double.parseDouble()：

// get the user input and put it into a string variable first
String userInput = JOptionPane.showInputDialog(null, "Please enter a kilometer value you wish to convert to miles;", HEADING,     JOptionPane.QUESTION_MESSAGE);
// parse the user's input and assign the result to kilometers
kilometers = Double.parseDouble(userInput);

Answer 2

Double.parseDouble（）是新变量的答案，允许用户输入转换为double！

字符串无法转换为双重错误的JOptionPane用于输入？

2 个答案: