java - 尽管通过 nextInt() 作为整数输入，但仍被接受为字符串

Question

import java.lang.String;
import java.lang.System;

import java.text.DecimalFormat;

import java.io.IOException;

import java.util.Scanner;

public class StorePrice
{
    public static void main (String args[]) throws IOException
    {
        int taxRate, markupRate, price;
        Scanner prompt = new Scanner(System.in);
        DecimalFormat decimal = new DecimalFormat("#,##0.00");

        System.out.print("Input the original price: ");
        price = prompt.nextInt();
        System.out.print("Input the markup rate: ");
        markupRate = prompt.nextInt();
        System.out.print("Input the tax rate: ");
        taxRate = prompt.nextInt();

        markupRate = decimal.format(markupRate);
        taxRate = decimal.format(taxRate);

        System.out.print("Original price: " + price + "\n");
        System.out.print("Markup rate: " + markupRate + "\n");
        System.out.print("Selling price: " + (price + (price*markupRate)) + "\n");
        System.out.print("Tax rate: " + taxRate + "\n");
        System.out.print("Tax: " + (price*taxRate) + "\n");
        System.out.print("Final price: " + ((price*markupRate) + (price*taxRate)) + "\n");
    }
}

您好，我是 OOP 和 Java 本身的新手，我在通过 nextInt(); 输入的数据类型时遇到问题。错误是这样的:

C:\Stuffs\Codes\Java\StorePrice.java:25: error: incompatible types
        markupRate = decimal.format(markupRate);
                                   ^
  required: int
  found:    String
C:\Stuffs\Codes\Java\StorePrice.java:26: error: incompatible types
        taxRate = decimal.format(taxRate);
                                ^
  required: int
  found:    String
2 errors

为什么输入的是整数还是字符串？问题出在哪里？

编辑:我忘记补充一点，我被严格指示在代码中将 price、markupRate 和 taxRate 声明为整数。

Answer 1

在将变量赋值给变量时，您必须了解所调用方法的返回类型(当它不是由您创建时，您可以在文档中查找)。在本例中，您尝试将 INT markupRate 和税率分配给从decimal.format(int) 返回的字符串变量。所以你要做的只是创建一些 String 变量来保存返回的字符串，但你仍然需要 int 作为参数进行格式化。试试这个:

    public static void main (String args[]) throws IOException
    {
       int  taxRate, markupRate, price;
        String sMarkupRate, sTaxRate;
        String sSellingPrice, sTax, sFinalPrice;
        Scanner prompt = new Scanner(System.in);
        DecimalFormat decimal = new DecimalFormat("#,##0.00");

        System.out.print("Input the original price: ");
        price = prompt.nextInt();
        System.out.print("Input the markup rate: ");
        markupRate = prompt.nextInt();
        System.out.print("Input the tax rate: ");
        taxRate = prompt.nextInt();

        sMarkupRate = decimal.format(markupRate);
        sTaxRate = decimal.format(taxRate);
        sSellingPrice = decimal.format(price + (price*markupRate));
        sTax = decimal.format((price*taxRate));
        sFinalPrice = decimal.format((price*markupRate) + (price*taxRate));


        System.out.print("Original price: " + price + "\n");
        System.out.print("Markup rate: " + sMarkupRate  + "\n");
        System.out.print("Selling price: " + sSellingPrice + "\n");
        System.out.print("Tax rate: " + sTaxRate + "\n");
        System.out.print("Tax: " + sTax + "\n");
        System.out.print("Final price: " + sFinalPrice + "\n");
    }
}