java - java中出现异常后如何重复特定语句？

Question

众所周知，当发生异常时，我们用“try and catch”捕获它，并且程序向前运行，但我希望程序从异常最初发生的位置开始运行。下面是我制作的迷你计算器的示例。当程序运行时，系统会要求用户输入整数选择号来选择程序的功能，例如加法、减法等。如果用户输入字符或字符串，则会发生异常，该异常会被捕获，程序会继续运行，用户可以重新启动该程序。但我希望当用户给出错误的输入导致异常时，程序从同一点运行，即输入您的选择号。选择功能。对于程序中的进一步输入也类似。谁能指导我吗？

package string;

import java.util.Scanner;
import java.lang.Exception;

public class Calculator2 {

    double sum(double number1, double number2) {
        double operation = number1 + number2;
        return operation;
    }

    double subtract(double number1, double number2) {
        double operation = number1 - number2;
        return operation;
    }

    double multiply(double number1, double number2) {
        double operation = number1 * number2;
        return operation;
    }

    double divide(double number1, double number2) {
        double operation = number1 / number2;
        return operation;
    }

    public static void main(String[] args) {
        Calculator2 f = new Calculator2();
        int choice;
        int z;

        Scanner s1 = new Scanner(System.in);

        do {
            try {
                System.out.println();
                System.out.println("Welcome To Sebiz Caculator:  Which Function Do You Want To Use");
                System.out.println("1.Addition");
                System.out.println("2.Subtraction");
                System.out.println("3.Multiplication");
                System.out.println("4.Division");
                System.out.println();
                System.out.print("Please Enter Your Choice Number: ");
                choice = s1.nextInt();

                System.out.println();
                System.out.print("Please Enter The First Number: ");
                double numb1 = s1.nextDouble();
                System.out.println();
                System.out.print("Please Enter The Second Number: ");
                double numb2 = s1.nextDouble();
                double result;
                String operation = "";

                switch (choice) {
                case 1:
                    result = f.sum(numb1, numb2);
                    operation = "Sum";
                    break;
                case 2:
                    result = f.subtract(numb1, numb2);
                    operation = "Substraction";
                    break;
                case 3:
                    result = f.multiply(numb1, numb2);
                    operation = "Multiplication";
                    break;
                case 4:
                    result = f.divide(numb1, numb2);
                    operation = "Divison";
                    break;
                default:
                    result = 0;
                    System.out.println();
                    System.out.println("Please Enter a Valid Choice from 1 to 4");
                }

                System.out.println();
                System.out.println("The " + operation + " Of Two Numbers is: "
                        + result);
            } catch (Exception e) {
                System.out
                        .println("You Have Entered An Invalid Input. Please Enter 1 On Next Instruction To Start Again");
                s1.nextLine();
            }
            System.out.println();
            System.out.println("Do You Want To perform Another Functionality?");
            System.out
                    .print("Press 1 to Continue and Press 2 to Terminate The Program ");
            z = s1.nextInt();
        } while (z == 1);

        System.out.println();
        System.out.println("Thank You For Using Sebiz Calculator");
    }
}

Answer 1

通过分离您的业务，您可以获得很多好处。您可以从扫描仪开始:

package string;

import java.util.Scanner;
import java.lang.Exception;

public class Calculator2
{

    Scanner s1 = new Scanner(System.in);

    double getIntInput(String message) {
        try {
            System.out.print(message);
            return s1.nextInt();
        }catch(Exception e) {
            System.out.print("There was an error in your input it is not an int, please try again");
            return getIntInput(message);
        }
    }

    double getDoubleInput(String message) {
        try {
            return s1.nextDouble();
        }catch(Exception e) {
            System.out.print("There was an error in your input it is not a double, please try again");
            return getDoubleInput(message);
        }
    }

    double sum(double number1, double number2) {
        double operation = number1 + number2;
        return operation;
    }

    double subtract(double number1, double number2) {
        double operation = number1 - number2;
        return operation;
    }

    double multiply(double number1, double number2) {
        double operation = number1 * number2;
        return operation;
    }

    double divide(double number1, double number2) {
        double operation = number1 / number2;
        return operation;
    }


    public static void main(String[] args){
        Calculator2 f = new Calculator2();
        int choice;
        int z;

        do
        {
            try
            {
                System.out.println();
                System.out.println("Welcome To Sebiz Caculator:  Which Function Do You Want To Use");
                System.out.println("1.Addition");
                System.out.println("2.Subtraction");
                System.out.println("3.Multiplication");
                System.out.println("4.Division");
                System.out.println();
                choice = getIntInput("Please Enter Your Choice Number: ");

                System.out.println();
                double numb1 = getDoubleInput("Please Enter The First Number: ");
                System.out.println();
                double numb2 = getDoubleInput("Please Enter The Second Number: ");
                double result;
                String operation = "";

                switch (choice)
                {
                    case 1:
                        result = f.sum(numb1, numb2);
                        operation = "Sum";
                        break;
                    case 2:
                        result = f.subtract(numb1, numb2);
                        operation = "Substraction";
                        break;
                    case 3:
                        result = f.multiply(numb1, numb2);
                        operation = "Multiplication";
                        break;
                    case 4:
                        result = f.divide(numb1, numb2);
                        operation = "Divison";
                        break;
                    default:
                        result = 0;
                        System.out.println();
                        System.out.println("Please Enter a Valid Choice from 1 to 4");
                }

                System.out.println();
                System.out.println("The " + operation + " Of Two Numbers is: " + result);
            }
            catch (Exception e)
            {
                System.out.println("You Have Entered An Invalid Input. Please Enter 1 On Next Instruction To Start Again");
                s1.nextLine();
            }
            System.out.println();
            System.out.println("Do You Want To perform Another Functionality?");
            System.out.print("Press 1 to Continue and Press 2 to Terminate The Program ");
            z = s1.nextInt();
        }
        while (z == 1);

        System.out.println();
        System.out.println("Thank You For Using Sebiz Calculator");
    }
}