如何处理java中的无效输入

Question

我正在制作一个简单的银行存款和取款代码。代码适用于存款部分，但在提款时它会询问提款值 2 次。取款金额取最后一个值。

我想我需要进入scannerObject.nextLine();某个地方，但是在哪里以及如何使用scannerObject.nextLine();？

以下是我的示例代码。还有一个其他类文件 BankAccount.java 只有 getter 和 setter 方法。

package com.amit;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        BankAccount account = new BankAccount();

        boolean option = true;

        Scanner scanner = new Scanner(System.in);

        while (option){

            System.out.println("Press 1 For Deposite. Press 2 For Withdrawal. Press 3 For Exit");

            boolean hasvalue = scanner.hasNextInt();

            if(hasvalue){

                //means user has entered integer value now check if its in 1, 2 if  its other

                // than this we'll take him out of program to print balance

                int userValEntered = scanner.nextInt();

                if (userValEntered == 1){

                    //code for deposite

                    System.out.println("Enter Amount To Deposite");

                    Scanner amountToDeposite = new Scanner(System.in);

                    account.setBalance(amountToDeposite.nextDouble());

                }else if (userValEntered == 2) {

                    //Code for withdrawal

                    System.out.println("Enter Amount To Withdraw");

                    Scanner amountToWithdraw = new Scanner(System.in);

                    if (amountToWithdraw.nextDouble() >= account.getBalance()){

                        System.out.println("Unable to Withdraw Given Amount, Try Other Amount");

                        continue;

                    }else {

                        double currentBalance = account.getBalance() - amountToWithdraw.nextDouble();

                        account.setBalance(currentBalance);

                        System.out.println("Thanks for Doing Business With us");

                    }

                }else{

                    //if user enters anything other than 1 or 2

                    break;

                }

            }

Answer 1

我发现我使用.nextDouble了两次的错误。从现在开始，我会确保在使用它之前先将它保存在变量中。这就是我更新代码的方式。package com.amit;import java.util.Scanner;public class Main {    public static void main(String[] args) {        BankAccount account = new BankAccount();        boolean option = true;        Scanner scanner = new Scanner(System.in);        while (option){            System.out.println("Press 1 For Deposite. Press 2 For Withdrawal. Press 3 For Exit");            boolean hasvalue = scanner.hasNextInt();            if(hasvalue){                //means user has entered integer value now check if its in 1, 2 if  its other                // than this we'll take him out of program to print balance                int userValEntered = scanner.nextInt();                if (userValEntered == 1){                    //code for deposite                    System.out.println("Enter Amount To Deposite");                    Scanner amountToDeposite = new Scanner(System.in);                    account.setBalance(amountToDeposite.nextDouble());                }else if (userValEntered == 2) {                    //Code for withdrawal                    System.out.println("Enter Amount To Withdraw");                    Scanner amountToWithdraw = new Scanner(System.in);                    double withdrawAmt = amountToWithdraw.nextDouble();                    if (withdrawAmt >= account.getBalance()){                        System.out.println("Unable to Withdraw Given Amount, Try Other Amount");                        continue;                    }else {                        double currentBalance = account.getBalance() - withdrawAmt;                        account.setBalance(currentBalance);                        System.out.println("Thanks for Doing Business With us");                    }                }else{                    //if user enters anything other than 1 or 2                    break;                }            }else {                //if user enters anything other than integer                break;            }        }        //code to print balance here.        System.out.println("Your Balance is: "+account.getBalance());    }}