Question

如果提示允许用户输入“add 1 2”

如何将此转换为1 + 2并输出答案？

“sub 1 2”相同到1-2

我知道可以拆分成数组来解决这个问题，但我的老师不会让我们这样做这个任务，我们所允许的只是使用if和for循环。

我对代码的想法如下，但它不会让我通过，因为双i = line.nextDouble（）将无法正常工作

import java.util.Scanner;

public class Shell {

public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.println("Welcome to CS302Shell! "
            + "Enter help for a list of commands or exit to end.");

    String command = input.next();
    String line = input.nextLine();

    if (command.equals("add")) {
        double i = line.nextDouble();
    }






} /** method */

} / ** class * /

Answer 1

您可以使用split方法将字符串拆分为正确的部分：

public static double calculate(String input) {

        // Here you splitt the input-String at every space. So you get 3 pieces
        String[] splitted = input.trim().replace(" +", " ").split(" ");

        // Set the different element-values to variables
        String operator = splitted[0];
        // Here you have to cast the String to double because you can't
        // calculate with a String
        double first;
        double second;

        //With this try-catch block you check if the numbers are really numbers.
        try {
            first = Double.valueOf(splitted[1]);
            second = Double.valueOf(splitted[2]);
        } catch (NumberFormatException ne) {
            System.err.println("Your input for one of the numbers was wrong");
            return 0;
        }
        // Now you check which operator the user wants and return the result.
        switch (operator) {
        case "add":
            return first + second;
        case "sub":
            return first - second;
        case "multiply":
            return first * second;
        case "divide":
            return first / second;

            // If de user has given a wrong input, the return is 0
        default:
            return 0;
        }
    }

    public static void main(String[] args) {
        System.out.println(calculate("add 1 2"));
    }

Answer 2

字符串解析：

int result = 0;
String[] data = "add 1 2".split(" ");
switch(data[0]) {
    case "add":
        int param1 = Integer.parseInt(data[1]);
        int param2 = Integer.parseInt(data[2]);
        result = param1 + param2;
        break;
    case "sub":
        //...
        break;
}

你明白了。
一些数据验证将是一个好主意。还有一些try / catch阻塞了parseInt调用，以确保当有人输入＆＃34;添加b＆＃34;时，程序不会爆炸。等...

Answer 3

你应该先发布你的尝试，这样我们才能更好地帮助你，但我认为这可能是你想要的。所有这些代码都假设您输入了正确的输入。

public int addInput(String input){
     inputs = inputs.replace("add ", "");
     String[] inputs = input.split(" ", 2);
     return Integer.parseInt(inputs[0])+Integer.parseInt(inputs[1]);
}

public int subInput(String input){
     inputs = inputs.replace("sub ", "");
     String[] inputs = input.split(" ", 2);
     return Integer.parseInt(inputs[0])-Integer.parseInt(inputs[1]);
}

认真地看到你的代码会很好。：）

你如何转换输入＆＃34;添加1 2＆＃34;到＆＃34; 1 + 2＆＃34;

3 个答案: