*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可以正常工作，直到我将其保存到文件中。当我重新打开应用程序时，帐号从头开始，即如果保存的帐户号码是 100,101，当我重新打开应用程序时，帐户号码又从 100 开始。请任何人帮助我从文件中读取，然后将其写回文件。*
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人可以帮助我找到解决方案
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);
}
}
}