無法讀取Java文件中的數字和值？

Question

首先請原諒我的錯誤輸入錯誤和張貼錯誤，因爲我是新手，並且仍在學習如何使用它。

我應該創建一個代碼，詢問用戶他是否想要存入或提取，然後要求他輸入文件名，然後使用裏面的信息添加到帳戶;無論如何，這段代碼大約有25％完成了，而且我在測試代碼時遇到了麻煩，因爲它在詢問我輸入時似乎沒有讀取文件的名稱，您是否知道可能會導致此問題的原因？任何建議或反饋？

import java.io.*; 
import java.util.*; 

public class read { 

    public static void main(String [] args) throws FileNotFoundException { 
     Double currentbalance = 500.00; 
     System.out.println("To deposit enter 1"); 
     System.out.println("To Withdrwawl enter 2"); 
     Scanner depositOrWithdrawl = new Scanner(System.in); 
     int choose = depositOrWithdrawl.nextInt(); 
     if(choose == 1) { 

      double currentBalance = 500.00; 
      System.out.println("your current balance is: $"+ currentBalance); 
      System.out.println("Please enter the file name to deposit: "); 
      Scanner deposit = new Scanner(System.in); 
      String depositAmount = deposit.nextLine(); 
      File depositFile = new File(depositAmount); 
      int nextLine = 1; 


      while(deposit.hasNextLine()){ 
       double numbers = deposit.nextDouble(); 
       System.out.println("You are about to add: $"+ numbers + " To your Balance"); 
       currentBalance = currentBalance + numbers; 
       System.out.println("Your current balance is: $" + currentBalance); 
       nextLine++; 
      } 

     } 
    } 

} 

順便說一句，如果你告訴我如何包含代碼的前幾行使用計算器正確

Answer 1

我在猜測您想要讀取該文件，但是您並未在程序中的任何位置執行此操作。此行File depositFile = new File(depositAmount);實際上並不讀取文件，它只創建一個File類對象。我強烈建議你google 如何閱讀java中的文件。關於這個問題有很多很好的教程。無論如何，下面的代碼應該可以幫助你做你正在做的事情： -

import java.io.BufferedReader; 
import java.io.File; 
import java.io.FileNotFoundException; 
import java.io.FileReader; 
import java.io.IOException; 
import java.util.Scanner; 
// It is a bad practice to start a Java class name with a lower case character 
public class IdentifiableImpl { 


public static void main(String[] args) throws FileNotFoundException { 
    Double currentbalance = 500.00; 
    System.out.println("To deposit enter 1"); 
    System.out.println("To Withdrwawl enter 2"); 
    Scanner depositOrWithdrawl = new Scanner(System.in); 
    int choose = depositOrWithdrawl.nextInt(); 
    if (choose == 1) { 

     double currentBalance = 500.00; 
     System.out.println("your current balance is: $" + currentBalance); 
     System.out.println("Please enter the file name to deposit: "); 
     // Scanner deposit = new Scanner(System.in); 
     String depositAmount = depositOrWithdrawl.nextLine(); 
     File depositFile = new File(depositAmount); 
     // Create a stream to read from a file 
     BufferedReader br = new BufferedReader(new FileReader(depositFile)); 
     // String st; 
     // int nextLine = 1; 
     String input; 
     // Read a file line by line 
     try { 
      while ((input = br.readLine()) != null) { 
       try { 
        // Convert read line into double 
        double numbers = Double.valueOf(input); 
        System.out.println("You are about to add: $" + numbers + " To your Balance"); 
        currentBalance = currentBalance + numbers; 
        System.out.println("Your current balance is: $" + currentBalance); 
        // nextLine++; 
       } 
// Handle bad input gracefully 
catch (NumberFormatException e) { 
        System.out.println("Seems like there is an invalid amount in input file." + input 
          + " Will not proceed further"); 
        break; 
       } 
      } 

     } catch (IOException e) { 
      e.printStackTrace(); 
     } finally { 
//Close the stream in finally block 
      if(br!=null){ 
       try { 
        br.close(); 
       } catch (IOException e) { 
        e.printStackTrace(); 
       } 
      } 
     } 
    } 
} 

} 

Answer 2

如果你希望你的循環掃描的文件，而不是標準輸入將是非常有益的，您需要先將掃描儀指向文件：

deposit = new Scanner(depositFile);