Java编程、货币计算器

Question

这个问题已经存在:

Scanner issue when using nextLine after nextXXX [duplicate]

已关闭 9 年前。

作为初学者，我无法真正理解这段代码中的问题:

package Currency;

import java.util.Scanner;

public class Currency {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        double value1 = 0.00, value2 = 0.00;
        String currency;

        System.out.print("Enter a value: ");
        value1 = input.nextDouble();
        System.out.print("USD or EUR: ");
        currency = input.nextLine();


        if(currency.equals("USD")){
            value2 = value1 * 0.734878047;
            System.out.println(value1 + "USD = " + value2 + " EUR. (Conversion rate: 1 USD = 0.734878047 EUR)");
        } else if (currency.equals("EUR")) {
            value2 = value1 * 1.36077;
            System.out.println(value1 + "EUR = " + value2 + " USD. (Conversion rate: 1 EUR = 1.36077 USD)");
        } else {
            System.out.println("Conversion rate: 1 USD = 0.734878047 EUR"
            + "\nConversion rate: 1 EUR = 1.36077 USD");
        }

        input.close();

    }

}

不知何故，它甚至不读取第二个输入，而只是打印最后一个输入。谁能帮我解决这个问题？ :)

提前谢谢您。

Answer 1

看起来input.nextLine();正在从用户在第一个提示后按回车键时读取换行符。

一个快速修复方法是在提示输入 USD 或 EUR 之前添加另一个 input.nextLine()“虚拟”调用:

package Currency;

import java.util.Scanner;

public class Currency {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        double value1 = 0.00, value2 = 0.00;
        String currency;

        System.out.print("Enter a value: ");
        value1 = input.nextDouble();
        input.nextLine();
        System.out.print("USD or EUR: ");
        currency = input.nextLine();

        if(currency.equals("USD")){
            value2 = value1 * 0.734878047;
            System.out.println(value1 + "USD = " + value2 + " EUR. (Conversion rate: 1 USD = 0.734878047 EUR)");
        } else if (currency.equals("EUR")) {
            value2 = value1 * 1.36077;
            System.out.println(value1 + "EUR = " + value2 + " USD. (Conversion rate: 1 EUR = 1.36077 USD)");
        } else {
            System.out.println("Conversion rate: 1 USD = 0.734878047 EUR"
                    + "\nConversion rate: 1 EUR = 1.36077 USD");
        }

        input.close();
    }
}