Question

大家好，我真的很接近完成这个但是我的for循环遇到了问题。我需要我的程序让用户输入'w'或'h'让他们输入新的体重或身高。当他们做我的循环似乎停止由于某种原因。

package Assignments;
import java.util.*;
public class assignment3 {


public static void main(String[] args) {

    //Scanner
    Scanner stdIn = new Scanner(System.in);

    //Variables
    final double METERS_TO_CM = 100;   // The constant to convert meters to centimeters
    final double BSA_CONSTANT = 3600;  // The constant to divide by for bsa
    double bmi;                        // Body Mass Index
    double weight;                     // Weight in kilograms
    double height;                     // Height in meters
    String classification;             // Classifies the user into BMI categories 
    double bsa;                        // Body surface area



    System.out.print("Welcome to the BMI and BSA Calculator to begin enter weight in kilograms.");
    weight = stdIn.nextDouble();
    System.out.print("Enter height in meters: ");
    height = stdIn.nextDouble();
    bmi = weight/(height*height);
    bsa = Math.sqrt(((height*METERS_TO_CM)*weight)/BSA_CONSTANT);


    if (bmi < 18.5)
    {
        classification = "Underweight";
    }
    else if (bmi < 25)
    {
        classification = "Normal";
    }
    else if (bmi < 30)
    {
        classification = "Overweight";
    }
    else
    {
        classification = "Obese";
    }
    System.out.println("Choose Options below to set height and weight");
    System.out.println("Your classification is: " + classification);
    System.out.println("(H)eight: " + height + " meters");
    System.out.println("(W)eight: " + weight + " kilograms");
    System.out.printf("BMI: %.1f\n", bmi);
    System.out.printf("BSA: %.2f\n", bsa);
    System.out.println("(Q)uit");

    do {


        String response = stdIn.next();

        if (response.charAt(0)== 'w') 
        {
            System.out.println("Enter new weight: ");
            weight = stdIn.nextDouble();
            System.out.println("Choose Options below to set height and weight");
            System.out.println("Your classification is: " + classification);
            System.out.println("(H)eight: " + height + " meters");
            System.out.println("(W)eight: " + weight + " kilograms");
            System.out.printf("BMI: %.1f\n", bmi);
            System.out.printf("BSA: %.2f\n", bsa);
            System.out.println("(Q)uit");
        }
        else if (response.charAt(0) == 'h')
        {
            System.out.println("Enter new height: ");
            height = stdIn.nextDouble();
            System.out.println("Choose Options below to set height and weight");
            System.out.println("Your classification is: " + classification);
            System.out.println("(H)eight: " + height + " meters");
            System.out.println("(W)eight: " + weight + " kilograms");
            System.out.printf("BMI: %.1f\n", bmi);
            System.out.printf("BSA: %.2f\n", bsa);
            System.out.println("(Q)uit");
        }
        else if (response.charAt(0)!= 'w')
        {
            System.out.println("That is not a valid choice try again");
            response = stdIn.next();
        }
        else if (response.charAt(0)!= 'h')
        {
            System.out.println("that is not a valid choise try again");
            response = stdIn.next();
        }
    } while (stdIn.next().compareToIgnoreCase("q")!=0);
}
}

Answer 1

通过执行stdIn.next().compareToIgnoreCase("q")!=0，您要求计算机从STDIN缓冲区中提取下一个值。这意味着在您完成处理后，While循环正在等待数据从STDIN进入，然后才决定继续处理。你最好让while循环连续运行while( true ) { ... }并检查输入值（当你要求H或W时）检查它是否是q。如果是，则让程序退出。

Answer 2

循环是什么？ - 没关系，因为它已被纠正

我确实看到了您的Scanner对象的潜在问题，但因为它没有处理行尾令牌，您可能想要调用stdIn.nextLine（）;每次调用stdIn.next（）之后;或者stdIn.nextDouble（）;，这样就可以正确处理行尾字符。

Answer 3

你在太多地方调用stdIn.next()：在循环开始时，在循环终止测试中，以及在最后两个分支中（顺便说一句，它们都应该由一个分支替换） else { ... }）。（循环是一个do循环，顺便说一下，不是for循环。）

另一个问题是使用Scanner混合输入并使用System.out输出。我建议在尝试通过扫描程序进行任何输入之前调用System.out.flush（）。

我的do-while循环不循环

3 个答案: