简单的 Java 布尔值

Question

我需要帮助来修复我的布尔值，我对编程很陌生，而且我教授的英语很差。

如果highway 是true，我需要将5 加到mpg，并在city 是false 时减2。

import java.util.Scanner;

public class AdvancedTripCalc {
    public static void main(String[] args) {
        // New Trip Calc.
        String firstname;
        int mpg;
        int miles;
        double price;
        double totalcost;

        Scanner in = new Scanner(System.in);
        System.out.println("Please enter your First Name");
        firstname = in.nextLine();
        System.out.println("Please enter the MPG of your car");
        mpg = in.nextInt();
        boolean highway = true;
        boolean city = false;
        if (highway == true) {
            mpg = mpg + 5;
        }
        if (city == false) {
            mpg = mpg - 2;
        }
        System.out.println("Enter true if trip is on the highway false if the trip is       in the city");
        in.nextBoolean();
        System.out.println("Please enter the Miles to be traveled");
        miles = in.nextInt();
        System.out.println("Please enter the price per gallon of gas");
        price = in.nextDouble();

        totalcost = miles * price / mpg;
        System.out.println("Your name is " + firstname);
        System.out.println("Your MPG is " + mpg);
        System.out.println("Your miles to be traveled is " + miles);
        System.out.println("Your price per gallon of gas is " + price);
        System.out.println("Your total cost is " + totalcost);
    }
}

Answer 1

创建一个布尔变量，例如boolean inCity;

将in.nextBoolean(); 更改为inCity = in.nextBoolean();

然后，在您获得输入值之后，您可以使用if 语句进行检查。在您的代码中，您在获得输入之前检查if 语句。

所以你会得到这个：

boolean inCity;
System.out.println("Are you in the city?(true/false): ");
inCity = in.nextBoolean(); //Store input in variable

if (inCity) { //If the condition is a boolean variable, you can type it like this(if (boolean) )
    mpg -= 2;//Same as mpg = mpg - 2;
} else { //if inCity is false:
    mpg += 5; //mpg = mpg + 5;
}

Answer 2

if (highway) { 
    mpg = mpg + 5;
}

if (!city) {
    mpg = mpg - 2;
}

应该是

if (highway) { 
    mpg = mpg + 5;
} else { //not highway, so city 
    mpg = mpg - 2;
}

现在您检查它是否是高速公路。如果是true，代码加5。然后你检查它是否不是一个城市。如果是false，则代码减2。

另外，您只能在提交后检查布尔值：

System.out.println("Enter true if trip is on the highway false if the trip is in the city");
boolean highway = in.nextBoolean();
if (highway) { 
    mpg = mpg + 5;
} else { //not highway, so city 
    mpg = mpg - 2;
}