我做了一個程序來計算銷售稅，當我把它放在1.0的稅率，它不加倍？

Question

/* 
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* and open the template in the editor. 
*/ 
package javaapplication19; 

import java.util.Scanner; 

/** 
* 
* @author joshu 
*/ 
public class JavaApplication19 { 

    /** 
    * @param args the command line arguments 
    */ 
    public static void main(String[] args) { 
     // also please don't block me this is my second time using this site 

    System.out.println("// SALES_TAX////////////////////////////////////"); 
    Scanner input = new Scanner(System.in); 
    String emailAddress; 
    double itemPrice, itemAmount, SALES_TAX; 

    System.out.println("How many item will you like to buy?"); 
    itemAmount = input.nextDouble(); 

    System.out.println("What is the price of the item?"); 
    itemPrice = input.nextDouble(); 

    System.out.println("Enter sales tax rate: "); 
    SALES_TAX = input.nextDouble(); 

    final Double SalesTaxRate = SALES_TAX * itemPrice; 
    double totalprice = SalesTaxRate + (itemPrice * itemAmount); 

    emailAddress = input.nextLine(); 
    System.out.println("Please enter emailAddress"); 
    emailAddress = input.nextLine(); 

    System.out.printf("Your total price is: $ %1.2f" + " a copy of this invoice" 
    + " will be emailed to: %s\n", 
    totalprice,emailAddress.toUpperCase()); 

    System.out.println("///////////////////////////////////////////"); 





    } 

} 

Answer 1

這條線是有問題對於初學者：

final Double SalesTaxRate = SALES_TAX * itemPrice; 
double totalprice = SalesTaxRate + (itemPrice * itemAmount); 

你只是增加稅率上的單個項目，總金額不。

Answer 2

我會改變邏輯您的總的計算，像這樣：

//gets the percentage of the item, and then adds the item price 
    final Double SalesTaxRate = itemPrice + (itemPrice * (SALES_TAX/100)); 

//simply multiply the new price by the amount required 
     double totalprice = SalesTaxRate * itemAmount;