Java Homework用户输入问题

Question

我有一个类分配来使用Scanner读取数据.

import java.util.Scanner;

public class Project23
{
    public static void main(String[] args)
    {
        // Declarations and instantiations.
        Scanner scan = new Scanner(System.in);
        String any = "";
        boolean more = false;
        double purchase = 0.0;

        // Ask if user would like to run program?
        System.out.print("Do you have any purchases? Y/N?: ");

        // Ready value into string.
        any = scan.nextLine();
        System.out.println();

        // If any is equal to y or Y it will set the value of more to true
        // this runs the while statement below.
        more = any.toUpperCase().equals("Y");

        // While more is still true continue to run the code within the brackets.
        while (more)
        {
            System.out.print("Please input purchase amount: ");
            purchase += scan.nextDouble();
            System.out.println();

            System.out.print("Do you have any more purchases Y/N?: ");
            any = scan.nextLine();
            System.out.println();

            more = any.toUpperCase().equals("Y");
        }

        if (purchase >= 2500)
            System.out.println("Purchase >= 2500");
        else
            System.out.println("Purchase < 2500");
    }
}

底部就是我的测试,以确定每个标志是否正常运行.然而我设置的while循环似乎不想继续运行多次.它将采用一个值,然后如果我说是我有更多的值(y或Y)它将退出并打印任何鲣鸟

Answer 1

基本上发生的事情是,当您正在读取double.inxtDouble()时,您只读取double,但是当您在scan.nextDouble()未读取的流上按Enter键时会出现ENDLINE字符.因此,当您到达any1 = scan.nextLine()时,它会读取不等于Y或y的结束字符.结果它退出while循环.像这样纠正你的代码,只需在你读正文的地方换一行:

while(more){

    System.out.print("Please input purchase amount: ");
    purchase+=Double.parseDouble(scan.nextLine());
    System.out.println();
    System.out.print("Do you have any more purchases Y/N?: ");
    // scan.nextLine();
    String any1=scan.nextLine();
    System.out.println();       
    more = any1.equals("y") || any1.equals("Y");//Shortened :)
}