Java 使用传入参数作为计算器的输入字符串执行计算

如果我运行计算器，我希望它开始自动计算给定参数，例如4+4-2。当没有参数时，他只要求用户插入数字（扫描仪）。这是我的代码。因此需要将参数分配给我的inputString。如果没有参数，扫描仪将要求用户输入一些内容

Main

计算器

package com.haynespro.calculator；
导入java.util.ArrayList；
公共类计算器{
公共无效起始计算器（字符串输入字符串）{
//将字符串“res”的ArrayList指定给splitExpression
ArrayList res=拆分表达式（inputString）；
//创建一个包含res的ObjectList
ArrayList objectList=新的ArrayList（res）；
System.out.print（“\n让我的算法处理它：\n\n”）；
//循环遍历objectList并将字符串转换为双精度字符串
对于（int i=0；i

您没有验证

args.length

以确定传入了多少个参数

我将给你一个简化的版本，因为我不知道你应该如何读取/解析args

字符串输入；
如果（参数长度<1）{
//您需要一个扫描仪来读取计算器的输入
输入=新扫描仪（System.in）.nextLine（）；
}否则{
//您需要分析args
input=String.join（“，args）；
}
新计算器（）.开始计算器（输入）；

使用args更改main（也可以在main类中进行一些重构）：

---

分享Calculator类的代码您几乎就要完成了您只需获取参数并将其传递给Calculator，如果没有参数，则您可以询问它们这是我的问题，因为新手我一直在接近解决方案，但无法获得完整的解决方案：（提示1:

inputString=inputString+arg+”；

即，添加（每个）arg后面跟一个空格，指向

inputString

（将其初始化为空）。提示2：要删除逗号的replace命令没有任何作用，因为此时字符串仅为

“0”

。您不必加入args，因为示例中没有空格“4+4-2”，仅足以使用args[0]@但一个例子只是一个例子，缺少规范，所以我们可以猜测……可能还需要对每个实例分别进行一次计算argument@Amirates但请删除多余的

替换
-
“0”
没有
，
（或在读取用户输入后移动，如有必要）
package com.haynespro.calculator;

import java.util.Scanner;

public class CharAtExample {

public static void main(String[] args) {

    for (String arg : args) {

        System.out.println(arg);


    }

    // inputString with scanner

    String inputString = "0";

    inputString = inputString.replace(",", "");

    Scanner userInput = new Scanner(System.in);

    System.out.print("please insert your calculations: ");

    inputString = userInput.next();

    userInput.close();

    Calculator calculator = new Calculator();

    calculator.startCalculator(inputString);

  }// end of main
}// end of class

package com.haynespro.calculator;

import java.util.ArrayList;

public class Calculator {

 public void startCalculator(String inputString) {

    // Assign ArrayList of Strings "res" to splitExpression

    ArrayList<String> res = splitExpression(inputString);

    // Create an ObjectList that holds res

    ArrayList<Object> objectList = new ArrayList<Object>(res);

    System.out.print("\nLet my algorithm take care of it: \n\n");

    // Loop through the objectList and convert strings to doubles

    for (int i = 0; i < objectList.size(); i++) {
        try {
            objectList.set(i, Double.parseDouble((String) 
  objectList.get(i)));
        } catch (NumberFormatException nfe) {

        }
    }

    // Create a variable maxi to substract 2 from the objectList index

    int maxi = objectList.size();

    maxi = maxi - 2;

    // Create variable lastSum out of the incoming for-loop's scope.

    double lastSum = 0;

    // Loop through the objectList with an algorhitm and perform 
    calculations with
    // invoking the sum method

    for (int i = 0; i < maxi; i += 2) {
        String operator = (String) objectList.get(i + 1);
        double a = (Double) objectList.get(i);
        double b = (Double) objectList.get(i + 2);
        double sum;

        if (i == 0) {
            sum = sum(a, b, operator);
        } else {
            sum = sum(lastSum, b, operator);
        }
        lastSum = sum;
        System.out.println(lastSum);
    }

}

// Method that matches the string input with operators to perform 
calculations.

public static double sum(Double a, Double b, String operator) {

    if (operator.equals("+")) {
        return a + b;
    }
    if (operator.equals("-")) {
        return a - b;
    }
    if (operator.equals("*")) {
        return a * b;
    }
    if (operator.equals("/")) {
        return a / b;
    }
    return 0;
}

// ArrayList splitExpression that casts to inputString

private static ArrayList<String> splitExpression(String inputString) {

    // ArrayList result to return the result

    ArrayList<String> result = new ArrayList<String>();

    // Uses the toCharArray method to insert the string reference per 
  character into
    // an array

    char[] destArray = inputString.toCharArray();

    // Empty String created

    String token = "";

    // Iterate through the "Items" in the Array

    for (int i = 0; i < destArray.length; i++) {

        // Nice all those references but we need an Object that actually 
 holds the array

        char c = destArray[i];

        // If not a number then add to token, else assign the value of c to 
 token

        if (isBreakCharacter(c)) {
            result.add(token);
            result.add(Character.toString(c));
            token = "";
        } else
            token = token + c;

    }

    result.add(token);
    return result;
}

// a method that breaks characters which are not numbers.The object "c" also
// needs to hold this method.

public static boolean isBreakCharacter(char c) {
    return c == '+' || c == '*' || c == '-' || c == '/';
}

}

String input;

if (args.length < 1) {
    // you need a Scanner to read an input for the calculator
    input = new Scanner(System.in).nextLine();
} else {
    // you've got args to parse
    input = String.join("", args);
}

new Calculator().startCalculator(input);

public static void main(String[] args) {
    String input=null;
    if(args.length>0){
        input=args[0];
        System.out.println(input);
    }else{
        input=askForInput();
    }

    Calculator calculator = new Calculator();

    calculator.startCalculator(input);

}// end of main

private static String askForInput() {
    // inputString with scanner
    Scanner userInput = new Scanner(System.in);
    System.out.print("please insert your calculations: ");
    String inputString;
    try {
        inputString = userInput.next();
    } finally {
        userInput.close();
    }
    return inputString;
}