十进制格式说“字符串不能转换为双精度”

问题描述

我正在尝试将球体的体积四舍五入到小数点后一位，但我不断收到错误消息，指出字符串无法转换为双精度。因此，我没有尝试格式化变量，而是输入一个数字来尝试查找问题，但它仍然说字符串无法转换为双精度值。我做错了什么，如何将我的变量格式化为一位小数？

import java.util.*;
import java.util.InputMismatchException;
import java.lang.Math.*;
import java.text.DecimalFormat;
public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        double diameter;
        DecimalFormat df = new DecimalFormat("#.#");



        //User Input Section
        while (true) {
        System.out.print("What is the diameter of the sphere (cm): ");
        try {
            diameter = input.nextDouble();
        break;  
        } catch (InputMismatchException mme) {
        System.out.println("Please enter a number in number format (e.x. 1,55,6)");
            input.nextDouble();
        }
        }
        
        double radius = diameter/2;
        double radiusCubed = radius * radius * radius;
        double radiusSquared = radius * radius;
        double fourOverThree = 4/3;

        double volumeOfSphere = fourOverThree * Math.PI * radiusCubed;
        double volumeOfSphere2 = df.format(1.1111111);
        double surfaceAreaOfSphere = 4 * Math.PI * radiusSquared;



        System.out.print("The volume of the sphere is " + volumeOfSphere2);
    

  }
}

解决方法

public class Pokecard { private String cardName; //Name of the Pokemon private String cardType; //Type of the card (Pokemon) private String pokemonType; //Type of the Pokemon (Example: Grass) private int hitPoints; //Hit points of the Pokemon private String pokemonAttacks; //What attacks the pokemon has private int cardNumber; //Number of the card (Example: 1) public void setPokemon(String name,String type,String pType,int hp,String attacks,int number) { this.cardName = name; this.cardType = type; this.pokemonType = pType; this.hitPoints = hp; this.pokemonAttacks = attacks; this.cardNumber = number; } } 返回一个 DecimalFormat.format。但是您将其分配给 String 变量。

将语句更改为：

double

在收到此类错误时，请阅读该方法可用的 javadoc 并检查返回类型/参数类型是否与您指定的匹配。

,

DecimalFormat.format() 方法返回一个字符串。您可以通过 Double.parseDouble() 方法将其解析使其翻倍。

double volumeOfSphere2 = Double.parseDouble(df.format(1.1111111));