java - Java 初级: Method doesn't recognise user input string passed to it

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这个问题已经有答案了:

已关闭 10 年前。

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String Comparison in Java…?

我正在解决一个我认为非常简单的问题......
带有硬编码产品列表的基本 101 购物车(仅限练习问题 - 我知道这不是真正的做法)

我希望用户输入一个字符串 - 产品代码，然后从描述方法获取关联产品的描述

它返回 0 值，即方法中的 if 语句似乎无法识别用户输入的字符串。

硬编码字符串有效 - 键盘输入的字符串无效我很困惑，但我认为我只是错过了一些基本的东西

import java.util.*;

class CW1ShoppingCart1_2ShowProdAndGetChoice
{
public static void main(String[] args)

{
/*PART 1 Offer catalogue and get user choice*/

System.out.println("ITEMS AVAIALBLE TODAY: \n");
System.out.print("P4383"+ "\t"+ CW1ShoppingCart1GetProductDetails.Description("P4383"));
System.out.println("\t"+ "$"+ CW1ShoppingCart1GetProductDetails.Price("P4383"));
System.out.print("P4385"+ "\t"+ CW1ShoppingCart1GetProductDetails.Description("P4385"));
System.out.println("\t"+ "$"+ CW1ShoppingCart1GetProductDetails.Price("P4385"));
System.out.print("P4387"+ "\t"+ CW1ShoppingCart1GetProductDetails.Description("P4387"));
System.out.println("\t"+ "$"+ CW1ShoppingCart1GetProductDetails.Price("P4387"));
System.out.println("\nTO START SHOPPING ENTER A PRODUCT CODE AND HIT RETURN \n");

Scanner in = new Scanner (System.in);
String ProdCode =in.nextLine();

System.out.println("You Chose: "+ CW1ShoppingCart1GetProductDetails.Description(ProdCode));

}
}

class CW1ShoppingCart1GetProductDetails
{

static String Description(String ProdCode)
{

String Proddesc;

if(ProdCode=="P4387")Proddesc = "Little used helper monkey - 1 ";
else if(ProdCode=="P4385") Proddesc = "Chilli chocolate - 100g ";
else if(ProdCode=="P4383")  Proddesc = "State-owned Bank - real value - 1 entity ";
else Proddesc = "0";

return Proddesc;
}

static double Price(String ProdCode)
{

double ProdPrice;

if(ProdCode=="P4387")  ProdPrice = 1200;
else if(ProdCode=="P4385") ProdPrice = 3.27;
else if(ProdCode=="P4383")  ProdPrice = -0.08;
else ProdPrice = 0;

return ProdPrice;
}

} 

Answer 1

问题是您正在使用 == 来比较字符串。请改用等于。

if(ProdCode.equals("P4387"))Proddesc = "Little used helper monkey - 1 ";

等等