Question

import java.util.Scanner;

public class AverageAndVariance {

public static void main (String[] args)
{
    System.out.println("This program computes the average and variance of all numbers entered. ");

    boolean finished = false;
    double total = 0.0;
    double average = 0.0;
    double variance = 0.0;

    Scanner inputScanner = new Scanner (System.in);

    while (!finished)
    {
        System.out.println("Enter a number (or type 'exit'): ");

        if (inputScanner.hasNextDouble())
        {   
            total++;

            double currentNum = inputScanner.nextDouble();
            average = (average) + (currentNum - average) / total;
            double prevAverage = ((average * total) - currentNum) / (total - 1);

            if (total > 1)
            {
                double var1 = (variance * (total - 1));
                double var2 = (currentNum - prevAverage) * (currentNum - average);  
                variance = (var1 + var2) / total;
            }

            System.out.println("So far the average is: " + average 
                                                    + "\nAnd the variance so far is: " + variance );        
        }
        else if (inputScanner.hasNext("exit"))
        {
            finished = true;
            System.out.println("Goodbye.");
            inputScanner.close();
        }
        else
        {
            System.out.println("Invalid input.");
        }
    }
}
}

只是想知道如何在最后处理错误，我的else语句是一个无限循环？如何让它回到while循环的开头？我觉得我的程序效率很低。我遇到方差的问题但是当我把嵌套的if语句放入其中时呢？我怎样才能使我的代码更有效率？感谢。

修改修复了无效的输入输出，只需将扫描仪放在while循环中，只是想知道这段代码是否比现在更有效？（即在保持相同功能的同时我可以删除任何if语句？）

Answer 1

在上面的代码中它很好但 inputScanner.hasNextDouble（）返回false我们输入错误的输入

import java.util.Scanner;

public class AverageAndVariance {

public static void main (String[] args)
{
    System.out.println("This program computes the average and variance of all numbers entered. ");

    boolean finished = false;
    double total = 0.0;
    double average = 0.0;
    double variance = 0.0;

    Scanner inputScanner = new Scanner (System.in);

    while (!finished)
    {
        System.out.println("1. Enter a number ");
        System.out.println("0. Exit ");
        System.out.println("Enter Your Choice ");
        try
        {
        int option= inputScanner.nextInt();

        switch(option)
        {
        case 1:
            total++;
            System.out.println("Enter your Number");
            double currentNum = inputScanner.nextDouble();
            average = (average) + (currentNum - average) / total;
            double prevAverage = ((average * total) - currentNum) / (total - 1);

            if (total > 1)
            {
                double var1 = (variance * (total - 1));
                double var2 = (currentNum - prevAverage) * (currentNum - average);  
                variance = (var1 + var2) / total;
            }

            System.out.println("So far the average is: " + average 
                                                    + "\nAnd the variance so far is: " + variance );       
            break;
        case 0:
            finished = true;
            System.out.println("Goodbye.");
            inputScanner.close();
            break;
        default:
            System.out.println("Invalid Output");
            break;
        }
        }
        catch(Exception ex)
        {
            System.out.println("Error "+ex.getMessage());
            finished = true;
        }

    }
}
}

错误处理和效率？

1 个答案: