Java 程序将无法识别标记值

Question

我的程序接受来自用户的输入数据（最多 20 个值）并计算 average/find 与平均值的距离。如果用户在尚未添加任何数字时输入“9999”，它将显示一条错误消息并告诉用户重新输入一个值。否则输入“9999”将收集用户输入的内容并进行计算。我的程序必须从用户那里收集所有 20 个输入，并且在完全输入值“9999”时也忽略它，但它会正确地进行其他计算。我不确定为什么它不承认我的哨兵价值。

package labpack;

import java.util.Scanner;

public class Lab4 {

    public static void main(String[] args) {
        int i = 0;
        double [] numbers = new double[20];
        double sum = 0;
        int sentValue = 9999;

        java.util.Scanner input = new java.util.Scanner(System.in);

        System.out.print("Enter the numbers you want up to 20");

        do {
            for (i = 0; i < numbers.length; i++) { 
                if (numbers[0] == sentValue){
                    System.out.println("Error: Please enter a number");
                    break;
                }
                else {
                    numbers[i] = input.nextDouble(); 
                    sum += numbers[i];
                }
            } 

            while (i<numbers.length && numbers[i]!=sentValue); //part of do-while loop

            //calculate average and distance from average
            double average = (sum / i);
            System.out.println("This is your average:" + average);

            for (i = 0; i < numbers.length; i++) { //Display for loop
                double diffrence = (average-numbers[i]);
                System.out.println("This is how far number " +numbers[i] +" is from the average:" + diffrence);
            }
        }
    }

Answer 1

您可以不执行 do-while 而是执行 while 来执行此操作。

if (numbers[0]== sentValue){
            System.out.println("Error: Please enter a number");
            break;

在这里，您试图在不使用用户输入初始化数组的情况下比较值。

这可以通过非常简单的方式完成：

import java.util.Scanner;
public class Lab4 {

    public static void main(String[] args) {
        int i = 0;
        double [] numbers =new double[10];
        double sum =0;
        double sentValue=9999;
        int count = 0;
        System.out.println(numbers.length);
        System.out.print("Enter the numbers you want up to 20");
        Scanner input = new Scanner(System.in);
        while (i<numbers.length){
            double temp = input.nextDouble();
            if (temp >= sentValue){
                if(i==0){
                    System.out.println("Error Message Here");
                } else {
                    break;
                }
            }//if
            else {
                numbers[i] = temp;
                sum += numbers[i];
                i++;
                count++;
            }
        } //part of while loop*/

        //calculate average and distance from average
        double average=(sum/i);
        System.out.println("This is your average:" + average);

        for (i=0;i < count;i++){ //Display for loop
            double diffrence = (average-numbers[i]);
            System.out.println("This is how far number " +numbers[i] +" is from the average:" + diffrence);
        }//for loop
    }//main bracket

}//class lab4 bracket

您需要将 input.nextDouble() 的值存储到变量中，因为当编译器读取 input.nextDouble() ，每次它都会要求用户输入。

PS。您不需要重新初始化这部分：

java.util.Scanner input = new java.util.Scanner(System.in);

上面一行可以简单地写成：

Scanner input = new Scanner(System.in);

因为您已经导入了扫描仪。

import java.util.Scanner;

希望这对您有所帮助:)

Java 程序将无法识别标记值

Java program will not recognize sentinel value

java

arrays

for-loop

do-while

sentinel