Java编程、货币计算器
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Java programming, currency calculator
提问by user3836013
As a beginner, i cannot really understand the issue in this code:
作为初学者，我无法真正理解此代码中的问题：
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();
}
}
Somehow, it doesnt even read the second input, but just prints last else. Can anyone help me to get this right? :)
不知何故，它甚至不读取第二个输入，而只是打印最后一个。谁能帮我解决这个问题？:)
Thank you in advance.
先感谢您。
回答by paubo147
in the ifclauses in both cases use currency.trim().equals(...to remove any whitespaces at the beginning or end of the String.
在这if两种情况下的子句中都currency.trim().equals(...用于删除字符串开头或结尾的任何空格。
回答by Aristocrates
It seems like input.nextLine();is reading in the newline from when the user hits enter after the first prompt.
input.nextLine();当用户在第一个提示后按回车键时，似乎正在读取换行符。
A quick fix could be adding in another input.nextLine()"dummy" call before you prompt for USDor EUR:
input.nextLine()在您提示USDor之前，快速修复可能是添加另一个“虚拟”调用EUR：
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();
}
}
回答by npinti
I think that hitting the return key is somewhat affecting the next readline. Doing a minor change as below seems to have fixed the problem:
我认为按下回车键在某种程度上影响了下一个阅读行。做一个如下的小改动似乎已经解决了这个问题：
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: ");
String str = input.nextLine();
value1 = Double.parseDouble(str);
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();
}
Example:
例子：
Enter a value: 25
USD or EUR: USD
25.0USD = 18.371951175 EUR. (Conversion rate: 1 USD = 0.734878047 EUR)
Alternatively, since in your case you are expecting a string without any white space, you could use the .next()property instead and leave your code as is:
或者，由于在您的情况下，您需要一个没有任何空格的字符串，您可以改用该.next()属性并按原样保留代码：
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.next();
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();
}
