Question

我正在学习Java，而且我很难理解为什么一个简单的程序我正在按照它应该的方式工作。

import java.util.Scanner;

class CarApp{
String carMake;
String carColour;
String features;
int carPrice;

void carFinal(){
    System.out.println(carMake);
    System.out.println(carPrice);
    if(carMake == "ford")
    {
        carPrice = 120000;
    }
    else if(carMake == "porsche")
    {
        carPrice = 1000000;
    }
    System.out.println(carPrice);
    System.out.println("Thank you for choosing your car with the car chooser app!" + "\n");
    System.out.println("You have chosen a " + carColour + " " + carMake + " with " + features + "\n" );
    System.out.println("Your car will be delivered to you in 7 working days. At a price of R" + carPrice + ".");
}
}

public class App {
public static void main(String[] args) {
    Scanner carChooser = new Scanner(System.in);

    CarApp carApp = new CarApp();
    System.out.println("Please let us know which car you would like, porsche or ford:");
    carApp.carMake = carChooser.nextLine();
    System.out.println("Please say which color car you would like:");
    carApp.carColour = carChooser.nextLine();
    System.out.println("Which features would you like added to your car:");
    carApp.features = carChooser.nextLine();
    carApp.carFinal();

}
}

系统似乎没有打印价格？所以我总是得到以下内容：

Your car will be delivered to you in 7 working days. At a price of R0.

任何帮助将不胜感激，我相信这是一件非常微不足道的事情，也许是我忽略的事情。提前谢谢，

佛瑞德

Answer 1

比较字符串时，您应该使用.equals。

例如：

if(carMake.equals("ford"))
{
    carPrice = 120000;
}
else if(carMake.equals("porsche"))
{
    carPrice = 1000000;
}

另外两个注意事项：

对于此用例，您可能希望使用.equalsIgnoreCase来检查相等性，忽略大小写。例如，无论用户是否输入“福特”，“福特”，“福特”，“福德”等，这都会触发第一种情况。
有些开发人员更喜欢使用Yoda Conditions约定，这会导致条件语写为if ("ford".equals(carMake))。与.equals等实例方法一起使用时，可以防止细微的NullPointerExceptions泄漏到您的代码中。与==运算符一起使用时，可以防止意外分配。

理解java条件

1 个答案: