Question

*如何增加从保存的文本文件中读取的数字？

我正在尝试将从文件中读取的帐号添加到数组中，当我向数组添加新数据时，帐号应该是现有帐号的自动增量。我的代码的问题是，它直到我将其保存到文件中才能正常运行。当我重新打开应用程序时，帐号从头开始，即如果保存的帐号是100,101，当我重新打开应用程序时，帐号从100再次开始。请任何人帮助我从文件中读取，然后将其写回文件。*

当重新启动应用程序时，数组从头开始。但我只是想知道是否有任何人可以帮我找到解决方案

这是我的代码

import java.io.Serializable;

public class Student implements Serializable {
    //--------------------------------------------------------------------------    
    protected static int nextBankID=1000;
    protected int accountNumber;    
    protected String fname;
    protected String lname;
    protected String phone;

    //--------------------------------------------------------------------------    
   //constructor
    public Student(String fname, String lname, String phone){

            this.accountNumber = nextBankID++;
            this.fname = fname;
            this.lname = lname;
            this.phone=phone;                 
    }
    //--------------------------------------------------------------------------
    public void setFname(String fname) {
        this.fname = fname;
    }
    //--------------------------------------------------------------------------
    public void setLname(String lname) {
        this.lname = lname;
    }
    //--------------------------------------------------------------------------
    public void setPhone(String phone) {
        this.phone = phone;
    }
    //--------------------------------------------------------------------------
    public int getAccountNumber() {
        return accountNumber;
    }
    //--------------------------------------------------------------------------
    public void setAccountNumber(int accountNumber) {
        this.accountNumber = accountNumber;
    }

    //--------------------------------------------------------------------------
    public String getFname() {
        return fname;
    }
    //--------------------------------------------------------------------------
    public String getLname() {
        return lname;
    }
    //--------------------------------------------------------------------------
    public String getPhone() {
        return phone;
    }  

    @Override
    public String toString(){

        return "\n #Acc\tFirst Name"+"\tLast Name\t#Phone"
        + "\tBalance"+ "\tOverdraft\t\t\n"+accountNumber+""
                + "\t"+fname+"\t"+lname+"\t"+phone; 
    }

}


//-------------------------------------------------------

import java.io.*;
import java.util.ArrayList;
import javax.swing.JOptionPane;

@SuppressWarnings("unchecked")

public class ReadWrite{

    //save stuAccount ArrayList will all stuAccount objects to file
public static void writeAccounts(String fileName,ArrayList<Student> stu) {
        //Create a stream between the program and the file
        try
        {
            FileOutputStream foStream = new FileOutputStream(fileName);
            ObjectOutputStream outStream = new ObjectOutputStream(foStream);

            outStream.writeObject(stu);
            outStream.close();
        }
        catch(FileNotFoundException fnfEx)
        {
              JOptionPane.showMessageDialog(null,fnfEx.getMessage());
        }
        catch(IOException ioE)
        {
               JOptionPane.showMessageDialog(null,ioE.getMessage());
        }   
}   

    //read stuAccount ArrayList
 public static ArrayList<Student> readAccounts(String fileName,ArrayList<Student> stu){ //throws IOException

     try
    {
    //JOptionPane.showMessageDialog(null, "Enter subject details to display");
            //StudentDriver.createSubject();  //create a subject to store stuAccount objects 
                FileInputStream fiStream = new FileInputStream(fileName);
                ObjectInputStream inStream = new ObjectInputStream(fiStream);

                stu = (ArrayList<Student>)inStream.readObject();
                //© Increment's the stu account with 1
                for (int i=0; i< stu.size(); i++){
                     Object b1 = stu.get(i);
                if (b1 instanceof Student){            
                    Student bAccount = (Student)b1;
                if(bAccount.accountNumber==stu.get(i).getAccountNumber())
                    bAccount.accountNumber=stu.get(i).getAccountNumber();
                    }

                }//for the next user entry
                inStream.close();

        }
        catch(ClassNotFoundException cnfEx){
            JOptionPane.showMessageDialog(null,cnfEx.getMessage());
        }       
        catch(FileNotFoundException fnfEx){
            JOptionPane.showMessageDialog(null,fnfEx.getMessage());
        }
        catch(IOException ioE){
            JOptionPane.showMessageDialog(null,ioE.getMessage());
        }

                JOptionPane.showMessageDialog(null, ""+stu.size()
                        + " stu account(s) found in the database....");

    return stu; //return read objects to Driver class   
 }
}


// ----------------------------------------------


import java.awt.Font;
import java.io.IOException;
import java.util.ArrayList;
import javax.swing.JOptionPane;
import javax.swing.JTextArea;

public class StudentDriver {

public static ArrayList<Student> stu = new ArrayList<>();
private static String fileName = "student.txt";

//------------------------------------------------------------------------------
public static void main(String [] vimal)  throws IOException{

   try{

           stu = ReadWrite.readAccounts(fileName,stu);

       if(stu.isEmpty()){
                JOptionPane.showMessageDialog(null,"No account's found "
                + "in the datbase to load into memory!\n\n");     
       }else{
            JOptionPane.showMessageDialog(null,"File contents "
                    + "read and loaded into memory!\n");
       }
    }
    catch (Exception e) {
                        JOptionPane.showMessageDialog(null,"Error encountered "
                                + "while opening the file"
                                + "\nCould not open file"
                                + "\n" + e.toString());
          } 
   //Initialise Main Menu Choice;              
//------------------------------------------------------------------------------           
    int choice= mainMenu();  

    while (choice!=3){

     switch (choice){
            case 1:
                createStudentAccount();//a new account Menu
                break;
            case 2:
                list();//list method            
                break;                  

            case -100:          
                    JOptionPane.showMessageDialog(null,"You have selected cancel");
                    break;          
            case -99:           
                    JOptionPane.showMessageDialog(null,"You must select  1-3");
                    break;          
            default:            
                    JOptionPane.showMessageDialog(null,"Not a valid option .Plese"
                                                        + " re-enter your option");
                    break;      
         }//END FO SWITCH STATEMENT 
      choice = mainMenu();
    }//END OF WHILE LOOP
   ReadWrite.writeAccounts(fileName,stu); //save ArrayList contents before exiting
    System.exit(0);                
   }    

//END MAIN , PROGRAM EXITS HERE 


public static int mainMenu(){

    String menu="US COLLEGE\n Main menu\n1.Add New Student\n2. Print All\n3. Exit\n\n";

    String userSelection = (String)JOptionPane.showInputDialog(null,menu);

        int option = validateSelection(userSelection);
    return  option;
}

//------------------------------------------------------------------------------
//                 CREATE ACCOUNT MENU SELECTION VALIDATION

public static int validateSelection(String createAccount){
    //enter cancel
    if (createAccount==null)
            return-100; 

    //hit enter without entry = zero-length string
    if (createAccount.length()<1)       
            return-99;

    //entered more than one charecter   
    if (createAccount.length()>1)       
            return-101;

    if (createAccount.charAt(0)< 49  || 
                                       createAccount.charAt(0)>51)      
            return-101;
    else    
            return Integer.parseInt(createAccount);
}


 public static void createStudentAccount(){

        String acctFirstName,acctLastName,strPhone;
        try{
                   //Account name validation
         acctFirstName = JOptionPane.showInputDialog(null,"Enter your first name");
         acctLastName = JOptionPane.showInputDialog(null,"Enter Your Family Name");
         strPhone =JOptionPane.showInputDialog(null,"Enter Your Phone nuber");


            stu.add(new Student(acctFirstName,
                                        acctLastName,strPhone));
     }
 catch(Exception e){}             
   }


public static void list(){

         String accounts = "";
         String College="\t======== US College ========\n";
         JTextArea output = new JTextArea();
         output.setFont(new Font("Ariel", Font.PLAIN, 12));  

if(stu.isEmpty()){
            JOptionPane.showMessageDialog(null,"No account's created yet");
         }
   else{      
         //for each Bank account in  BankAccount ArrayList
         for (Student s1: stu){         
         if(stu.isEmpty()){
                JOptionPane.showMessageDialog(null,"No account's created yet");               
         }else{              
             accounts += s1.toString();          
              } 
         output.setText(College+accounts );         
        }
         JOptionPane.showMessageDialog(null,output);
    }
  }
}

Answer 1

首先创建一个用于维护帐号的表。在将文本写入文件后，每次都使用通过递增帐号的值来更新以前帐号的表号为no。

如何从保存的文本文件中增加一个数字？

1 个答案: