如何使用Java检测Windows文本文件中是否有最近的更改

Question

Hi guys I am writing a small application in java where it reads a text file and parses the contents. My problem is my program will keep on reading the file because its inside a loop. My solution was to implement similar to what I usually do in linux like (see below)

ls -l -ctime 
or 
ls -l -atime

where it detects when the files was last accessed or written If you solution can be done in java or some windows command can you please let me know. Thanks

Update:

Thanks very much for helping

Westons Solution

public static long checkLastFileModification() throws InterruptedException{

    File file = new File(fileName);
    long lastProcessed = -1;

    while (true){
        long lastModified = file.lastModified();

        if (lastProcessed != lastModified){
            lastProcessed = lastModified;
            System.out.println("Last accessed : " + lastModified);
            //read the file in reverse order

        }
        else{
            System.out.println("No file access.... sleeping for 5 secs ");
            Thread.sleep(5000);
        }
    }

}

Answer 1

If you want to show it every single loop, then make a batch file named "loop.bat" in the same folder the project/program is. loop.bat must have the following contents:

@echo off
goto loop
:loop
cls
title Seeing file's contents.
type filename.txt
goto loop

And rename "filename.txt" with the text file you want to see. Now make a java code to show text that it has a batch file running seeing the contents of the file. Or if you can, print the text on the batch file to the java.

filename.txt, loop.bat and your java program must be in the same folder.

Answer 2

You can inspect the last modified time of the file:

new File(fileName).lastModified()

In your loop you can see if it is different:

long lastProcessed = -1;
File file = new File(fileName);
while(true) {
   long lastModified = file.lastModified();
   if (lastProcessed != lastModified) {
      lastProcessed = lastModified;
      process(file);
   }
   else {
     //some delay or sleep, else you're thrashing the thread and file
   }
}

Answer 3

I would suggest to use WatchService API.See in below exmple.

http://java.dzone.com/news/how-watch-file-system-changes

See API :- WatchService