[英]I can't figure out why overwriting a file's contents with an array results in an empty file
所以我修復了覆蓋問題,但現在問題是它吃掉了文本文件的最后一行。 或者我想它只是沒有把它寫回文件。 有任何想法嗎? 第一種方法應該將密碼更改為隨機密碼,第二種方法只是用於計算文本文件中的行數。
/**
* Method for resetting a password
* Replaces current password with randomly generated one.
*
* @param testUserName is the username used for finding the password
* to replace
*/
public String resetPassword(String testUserName) throws IOException {
int fileLength = countLines();
FileReader fr = new FileReader("Password.txt");
BufferedReader br = new BufferedReader(fr);
String[] storeData = new String[fileLength];
Random rand = new Random();
int pwNumber = (int)(rand.nextDouble() * 10000);
String pwReset = "Password" + pwNumber;
for (int i=0; i < fileLength; i ++) {
storeData[i] = br.readLine();
}
fr.close();
for (int i=0; i < (fileLength-1); i += 4) {
if (testUserName.equals(storeData[i])) {
storeData[i+1] = pwReset;
}
}
PrintWriter reset = new PrintWriter("Password.txt");
for (int i=0; i < fileLength; i ++) {
reset.println(storeData[i]);
}
reset.close();
return pwReset;
}
/**
* Method for counting number of lines in a file
* Used in conjuction with other methods for reading
* specific lines of files.
*/
public int countLines() throws IOException {
InputStream is = new BufferedInputStream(new FileInputStream("Password.txt"));
try {
byte[] c = new byte[1024];
int count = 0;
int readChars = 0;
boolean empty = true;
while ((readChars = is.read(c)) != -1) {
empty = false;
for (int i = 0; i < readChars; ++i) {
if (c[i] == '\n')
++count;
}
}
return (count == 0 && !empty) ? 1 : count;
} finally {
is.close();
}
}
我懷疑你countLines()方法正在重新讀取文件以確定那一刻的行數。 這不僅非常低效,而且還是您的bug的來源。
PrintWriter reset = new PrintWriter("Password.txt");
// file is now truncated.
countLine() == 0
我建議你計算一次的行數。 理想情況下,當你讀一次。
你可以改進它
。
public String resetPassword(String testUserName) throws IOException {
File passwdFile = new File("Password.txt");
BufferedReader br = new BufferedReader(new FileReader(passwdFile));
File tmpPasswdFile = new File("Password.txt.tmp");
PrintWriter reset = new PrintWriter(tmpPasswdFile);
String pwReset = null;
try {
boolean resetNextLine = false;
for (String line; (line = br.readLine()) != null; ) {
if (resetNextLine) {
Random rand = new Random();
int pwNumber = (int) (rand.nextDouble() * 10000);
pwReset = "Password" + pwNumber;
reset.println(pwReset);
} else {
reset.println(line);
}
resetNextLine = testUserName.equals(line);
}
} finally {
reset.close();
br.close();
}
passwdFile.delete();
tmpPasswdFile.renameTo(passwdFile);
return pwReset;
}
countLines()
如何工作?
我對這種方法有點懷疑,因為你正在使用它的結果迭代你的數組。 我本以為使用它的長度迭代數組可能更直觀(也更正確?)
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