[英]How to edit record in a text file using java?
我有一個文本文件,其中包含以下記錄:
JOHNY 412563
SARAH 147852369
這些記錄定義用戶帳戶的用戶名和密碼。
我編寫了一種簡單的方法來編輯記錄的密碼。
編輯密碼的方法是發送要編輯的用戶名和新密碼,然后該方法應制作該密碼的版本。 但是什么也沒發生,它會將新數據復制到臨時文件中,但不會再次復制到主文件中。
這是我寫的方法:
public int change_pass(String username, String password) {
boolean checked = true;
try {
File f = new File("C:\\Users\\فاطمة\\Downloads\\accounts.txt");
File tempFile = new File("C:\\Users\\فاطمة\\Downloads\\accounts2.txt");
BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));
Scanner sc = new Scanner(f);
Scanner sc2 = new Scanner(System.in);
while(sc.hasNextLine()) {
String currentLine = sc.nextLine();
String[] tokens = currentLine.split(" ");
if(Objects.equals(tokens[0], username) && checked) {
currentLine = tokens[0]+" "+password;
checked = false;
}
writer.write(currentLine + System.getProperty("line.separator"));
}
writer.close();
sc.close();
f.delete();
boolean successful = tempFile.renameTo(f);
if(successful == true) {
return 1;
} catch(Exception e) {
e.printStackTrace();
}
return 0;
}
這是我寫的主要程序:
Scanner sc = new Scanner(System.in);
String newpass = null;
System.out.println("Change account password !!");
System.out.println("Validate your account please !!");
System.out.printf("Username: ");
a1.setUsername(sc.next().toUpperCase());
System.out.printf("Old Password: ");
a1.setPassword(sc.next());
Scanner y = null;
try{
y = new Scanner(new File("C:\\Users\\?????\\Downloads\\accounts.txt"));
boolean checkaccount = false;
while(y.hasNext()) {
String a = y.next();
String b = y.next();
if((a == null ? a1.getUsername() == null : a.equals(a1.getUsername())) && (b == null ? a1.getPassword() == null : b.equals(a1.getPassword())))
checkaccount = true;
}
if(checkaccount) {
System.out.println("Your account has been verified successfully.");
} else
System.out.println("Wrong username or password ... try again.");
System.out.printf("New Password: ");
newpass = sc.next();
if(newpass.length() >= 6) {
if(c1.change_pass(a1.getUsername(), newpass) == 1)
System.out.println("Password has been changed successfully.");
else
System.out.println("Error occurred during changing password, try again.");
} else
System.out.println("Short password: password must be at least 6 characters.");
} catch(Exception e) {
e.printStackTrace();
}
經過很長一段時間,我終於找到了我的問題的解決方案:
非常簡單:只需添加以下行:
y.close();
前行:
if(checkaccount)
解釋:嘗試編輯文件時文件仍處於打開狀態。 因此,它會產生錯誤,並且必須先關閉它才能進行編輯。
因此,您必須在編輯之前關閉文件。
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