java - 如何允许java程序预定义数量的条目

Question

我的程序允许用户输入 20 个条目。每个条目都作为一个条目输入，然后从命令行按 Enter 键。我想添加程序的能力“您还剩 20 个条目”然后“您还剩 19 个条目”等等...当用户在程序中输入更多数据时。

如果有人能向我展示将其添加到我当前代码中的最简单方法，我将不胜感激。

import java.util.ArrayList;
import java.util.Scanner;

class project02Diaz
{   
    private static Double calculate_average( ArrayList<Double> myArr )
    {
        Double sum = 0.0;
        for (Double number: myArr)
        {
            sum += number;
        }
        return sum/myArr.size(); 
    }

    public static void main( String[] args )
    {
        Scanner           scan  = new Scanner(System.in);
        ArrayList<Double> myArr = new ArrayList<Double>();
        int               count = 0;

        System.out.println("Enter one number at a time be averaged, you have 20 entries remaining:");

        for (String inputs = scan.nextLine() ; !inputs.matches("[qQ]")  ; inputs = scan.nextLine())
        {
            if (count == 20)
            {
                System.out.println("You entered more than 20 numbers, you suck!");
                break;
            }
            try{
                myArr.add(Double.valueOf(inputs));
                count++; 
                System.out.println("Please enter another number or press Q for your average");
            }
            catch (NumberFormatException e) {
                System.out.println("Try again you tard! You entered more than one number, or not a valid number at all.");
                continue;                   
            }      

        }
        Double average = calculate_average(myArr);
        System.out.println("Your average is: " + average);
    }
}

Answer 1

又是你!好吧，我也要做这个。您无需更改太多内容:只需从 20 开始倒数计数器并每次输出 stauts 即可。另外，如果达到 0，请停止。

public static void main( String[] args )
{
    Scanner           scan        = new Scanner(System.in);
    ArrayList<Double> myArr       = new ArrayList<Double>();
    int               entriesLeft = 20; // changed counter that counts upwards to one counting down.

    System.out.println("Enter one number at a time be averaged, you have 20 entries remaining:");

    // added additional condition to be checked: we now also stop if maximum number of entries ie reached.
    for (String inputs = scan.nextLine() ; entriesLeft > 0 && !inputs.matches("[qQ]")  ; inputs = scan.nextLine())
    {
        try{
            myArr.add(Double.valueOf(inputs));
            entriesLeft--; //counting one down
            System.out.println("Please enter another number or press Q for your average");
            // telling user how much numbers are left
            System.out.println("You have " + entriesLeft + "numbers left.");
        }
        catch (NumberFormatException e) {
            System.out.println("Try again you tard! You entered more than one number, or not a valid number at all.");
            continue;                   
        }      

    }
    Double average = calculate_average(myArr);
    System.out.println("Your average is: " + average);
}

请注意，将整数 entriesLeft 附加到字符串并不是非常高效，更好的方法是调用 Integer.toString(entriesLeft)。