Question

抱歉这个菜鸟问题。这是我尝试Java编程的第一天。我需要帮助检索用户想要使用整数运算符的用户输入。

import java.util.Scanner;

public class calculator {

    public static void main (String args[]) {

        Scanner number = new Scanner(System.in);
        double num1,num2,answer;
        char operator;

        System.out.println("Enter first number: ");
        num1 = number.nextDouble();

        operator = number.nextChar(); /* the "nextChar" is not correct */

        System.out.println("Enter second number: ");
        num2 = number.nextDouble();

        if (operator = '+'){
            answer = num1 + num2; /* If statements do not work like this */
        }                             /* I would use "else if", unsure if it allows */
        if (operator = '-'){
            answer = num1 - num2;
        }
        if (operator = '*'){
            answer = num1 - num2;
        }
        if (operator = '/'){
                answer = num1 / num2;
        }

        System.out.println(num1 + num2 + operator + answer);

    }
}

编辑版本：

import java.util.Scanner;

public class calculator{

    public static void main (String args[]) {

        Scanner userInput = new Scanner(System.in);

        String operator;
        double num1,num2,answer = 0;



        System.out.println("Enter first number: ");
        num1 = userInput.nextDouble();

        System.out.println("Enter operator: ");
        operator = userInput.next();


        System.out.println("Enter second number: ");
        num2 = userInput.nextDouble();

        if (operator.equals ("+")){
            answer = num1 + num2;
        }
        else if (operator.equals ("-")){
            answer = num1 - num2;
        }
        else if (operator.equals ("*")){
            answer = num1 * num2;
        }
        else if (operator.equals ("/")){
                answer = num1 / num2;
        }

        System.out.println("First number:" + num1);
        System.out.println("Operator:" + operator);
        System.out.println("Second number:" + num2);

        System.out.println("Answer: " + answer);
    }
}

第一个数字：10.0

操作：*

第二个数字：3.14

答案：31.400000000000002

非常感谢！帮了很多忙！

Answer 1

在比较中使用==，而不是=（这意味着分配）。

Answer 2

正如其他人已经指出的那样，使用==运算符来检查是否相等。 =运算符将改为赋值。

要阅读Scanner中的单个字符，请查看以下问题：Scanner method to get a char。在那里你会发现使用Scanner.findInLine()方法的建议，它接收正则表达式作为参数。提供.通配符作为模式，您将能够获得包含下一个字符的字符串，并在其上使用charAt(0)，您将获得char。

Scanner sc = new Scanner("abc");
char ch = sc.findInLine(".").charAt(0);
System.out.println(ch); // prints "a"

当然，您也可以使用Scanner.next()将下一个单词作为String，并获取其第一个字符。但是考虑到这样做会从输入缓冲区丢弃其余部分。

Answer 3

确定。这有效，可以帮助您走向java

public class Tester4 {

    public static void main(String args[]) {

        Scanner input = new Scanner(System.in);
        double num1, num2, answer = 0;
        String operator;

        System.out.println("Enter first number: ");
        num1 = input.nextDouble();

        System.out.println("Enter operator: ");
        operator = input.next();

        System.out.println("Enter second number: ");
        num2 = input.nextDouble();

        if(operator.equals("+")) {
            answer = num1 + num2;
        } else if(operator.equals("-")) {
            answer = num1 - num2;
        } else if(operator.equals("*")) {
            answer = num1 - num2;
        } else if(operator.equals("/")) {
            answer = num1 / num2;
        }

        System.out.println("First number:" + num1);
        System.out.println("Operator:" + operator);
        System.out.println("Second number:" + num2);

        System.out.println("Answer: " + answer);
    }

}

Answer 4

您需要使用

if (operator == '+')

注意'double等于'。

从Scanner读取一个字符

4 个答案: