已经意识到，因为 发件人帐户ID 和 收件人帐户ID 在记录中，除非有分隔符保留在指示Null值的位置，否则没有真正的方法可以知道哪个ID可能丢失。但是，有可用的机制来确定确实是缺少的两种机制之一，这需要通过用户审查来进行，即使那样，可能可能还不够好。其他记录列字段，例如 金额 和 转帐日期 ，可以轻松地进行验证，或者如果缺少则可以暗示特定的文件数据状态日志。
下面是一些代码，该代码将读取数据文件（名为Data.csv）并将潜在的数据行（记录）错误记录到列表接口对象中，该对象将在读取完成后循环并显示在控制台窗口中。还有一些小的辅助方法。这是代码：
private void checkDataFile(String filePath) {
String ls = System.lineSeparator();
List<String> validationFailures = new ArrayList<>();
StringBuilder sb = new StringBuilder();
// 'Try With Resources' used here to auto-close reader.
try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
String line;
int lineCount = 0;
// Read the file line-by-line.
while ((line = reader.readLine()) != null) {
line = line.trim();
lineCount++;
if (lineCount == 1 || line.equals("")) {
continue;
}
sb.delete(0,sb.capacity()); // Clear the StringBuilder object
// Start the Status Log
sb.append("File Line Number: ").append(lineCount)
.append(" (\"").append(line).append("\")").append(ls);
// Split line into an Array based on a comma delimiter
// reguardless of the delimiter's spacing situation.
String[] lineParts = line.split("\\s{0,},\\s{0,}");
/* Validate each file line. Log any line that fails
any validation for any record column data into a
List Interface object named: validationFailures
*/
// Are there 4 Columns of data in each line...
if (lineParts.length < 4) {
sb.append("\t- Invalid Column Count!").append(ls);
// Which column is missing...
// *** You may need to add more conditions to suit your needs. ***
if (checkAccountIDs(lineParts[0]) && lineParts.length >= 2 && !checkAccountIDs(lineParts[1])) {
sb.append("\t- Either the 'Sender Account ID' or the "
+ "'ReceiverAccountID' is missing!").append(ls);
}
else if (lineParts.length >= 3 && !checkAmount(lineParts[2])) {
sb.append("\t- The 'Amount' value is missing!").append(ls);
}
else if (lineParts.length < 4) {
sb.append("\t- The 'Transfer Date' is missing!").append(ls);
}
}
else {
// Is SenderAccountID data valid...
if (!checkAccountIDs(lineParts[0])) {
sb.append("\t- Invalid Sender Account ID in column 1! (")
.append(lineParts[0].equals("") ? "Null" :
lineParts[0]).append(")");
if (lineParts[0].length() < 9) {
sb.append(" <-- Not Enough Or No Digits!").append(ls);
}
else if (lineParts[0].length() > 9) {
sb.append(" <-- Too Many Digits!").append(ls);
}
else {
sb.append(" <-- Not All Digits!").append(ls);
}
}
// Is ReceiverAccountID data valid...
if (!checkAccountIDs(lineParts[1])) {
sb.append("\t- Invalid Receiver Account ID in coloun 2! (")
.append(lineParts[1].equals("") ? "Null" :
lineParts[1]).append(")");
if (lineParts[1].length() < 9) {
sb.append(" <-- Not Enough Or No Digits!").append(ls);
}
else if (lineParts[1].length() > 9) {
sb.append(" <-- Too Many Digits!").append(ls);
}
else {
sb.append(" <-- Not All Digits!").append(ls);
}
}
// Is Amount data valid...
if (!checkAmount(lineParts[2])) {
sb.append("\t- Invalid Amount Value in column 3! (")
.append(lineParts[2].equals("") ? "Null" :
lineParts[2]).append(")").append(ls);
}
// Is TransferDate data valid...
if (!checkTransferDate(lineParts[3],"yyyy-MM-dd HH:mm:ss")) {
sb.append("\t- Invalid Transfer Date Timestamp in column 4! (")
.append(lineParts[3].equals("") ? "Null" :
lineParts[3]).append(")").append(ls);
}
}
if (!sb.toString().equals("")) {
validationFailures.add(sb.toString());
}
}
}
catch (FileNotFoundException ex) {
System.err.println(ex.getMessage());
}
catch (IOException ex) {
System.err.println(ex.getMessage());
}
// Display the Log...
String timeStamp = new SimpleDateFormat("yyyy/MM/dd - hh:mm:ssa").
format(new Timestamp(System.currentTimeMillis()));
String dispTitle = "File Data Status at " + timeStamp.toLowerCase()
+ " <:-:> (" + filePath + "):";
System.out.println(dispTitle + ls + String.join("",Collections.nCopies(dispTitle.length(),"=")) + ls);
if (validationFailures.size() > 0) {
for (String str : validationFailures) {
if (str.split(ls).length > 1) {
System.out.println(str);
System.out.println(String.join("",Collections.nCopies(80,"-")) + ls);
}
}
}
else {
System.out.println("No Issues Detected!" + ls);
}
}
private boolean checkAccountIDs(String accountID) {
return (accountID.matches("\\d+") && accountID.length() == 9);
}
private boolean checkAmount(String amount) {
return amount.matches("-?\\d+(\\.\\d+)?");
}
private boolean checkTransferDate(String transferDate,String format) {
return isValidDateString(transferDate,format);
}
private boolean isValidDateString(String dateToValidate,String dateFromat) {
if (dateToValidate == null || dateToValidate.equals("")) {
return false;
}
SimpleDateFormat sdf = new SimpleDateFormat(dateFromat);
sdf.setLenient(false);
try {
// If not valid,it will throw a ParseException
Date date = sdf.parse(dateToValidate);
return true;
}
catch (ParseException e) {
return false;
}
}
我不确定您的特定应用程序最终将要包含什么内容，但是如果其他进程正在访问文件并对其进行修改，则可能明智地利用锁定当您在特定过程中 Lock 锁定文件并在完成后 Unlock 锁定文件。但是，这很可能需要您使用其他读取算法，因为锁定文件必须通过 可写 通道来完成。使用 java.nio 包中的FileChannel和FileLock类可能在这里为您提供帮助。在StackOverflow论坛中将有一些示例，说明如何利用这些类。