拆分字符串 Java 计算器

Question

我有这个代码

错误出现在关于 -、* 和 / 操作的 if 语句中 "The operator / is undefined for the argument type(s) java.lang.String, java.lang.String" 谁能帮忙

Answer 1

您必须解析每个部分才能对它们执行数学运算。您不能对字符串执行此类操作（但您可以使用“+”连接字符串，但不能使用总和）。像这样：

import java.util.Scanner;

public class Calculator {    
    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in) ;
        System.out.println("Enter your two numbers and the operation with spaces between e.g 8 9 -");

        String calculation=scan.nextLine();

        String [] parts = calculation.split(" ");

        int part1 = Integer.parseInt(parts[0]);
        int part2 = Integer.parseInt(parts[1]);

        int answer;
        String operation = parts[2];
        switch (operation) {
            case "+":
                answer = part1 + part2;
                break;
            case "-":
                answer = part1 - part2;
                break;
            case "*":
                answer = part1 * part2;
                break;
            case "/":
                answer = part1 / part2;
                break;
            default:
                throw new IllegalStateException("Incorrect operation: " + operation);
        }

        String ans = String.valueOf(answer);
        System.out.println(ans);
    }    
}

如果你想打印错误的操作符号，你必须修改程序。首先，我们需要将整数 answer 变量初始化为“0”，并且您需要创建新的布尔变量来标记操作的正确性。

import java.util.Scanner;

public class Calculator {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in) ;
        System.out.println("Enter your two numbers and the operation with spaces between e.g 8 9 -");

        String calculation=scan.nextLine();

        String [] parts = calculation.split(" ");

        int part1 = Integer.parseInt(parts[0]);
        int part2 = Integer.parseInt(parts[1]);

        int answer = 0;
        boolean incorrectOperation = false;
        String operation = parts[2];
        switch (operation) {
            case "+":
                answer = part1 + part2;
                break;
            case "-":
                answer = part1 - part2;
                break;
            case "*":
                answer = part1 * part2;
                break;
            case "/":
                answer = part1 / part2;
                break;
            default:
                incorrectOperation = true;
        }

        String ans;
        if(incorrectOperation) {
            ans = "Incorrect operation: " + operation;
        } else {
            ans = String.valueOf(answer);
        }

        System.out.println(ans);
    }
}

Answer 2

除了使用 Integer.parse()，为什么不在您的用例中使用 scanner.nextInt()？

    int part1 = scan.nextInt();
    int part2 = scan.nextInt();
    String operation = scan.nextLine().trim();

拆分字符串 Java 计算器

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