how to make readLine() of Filereader to go to previous location

I am creating one text file which will connected to some server. this text file will receive its contents from the server. It will receive the some text data continuously.

To limit the file size , I am checking no.of lines in the file and if exceeds the mark I am clearing file content. Server will write from the beginning.

Below is the code I have used to do this :

LineNumberReader myReader = new LineNumberReader( new FileReader(new File("mnt/sdcard/abc.txt")));
while(true) {   

    while(myReader.readLine() != null) {
        counter ++;
    }

    if(counter > 100 ) {

        PrintWriter writer = new PrintWriter("/mnt/sdcard/abc.txt");
                    writer.print("");
                    writer.close();
                    writer = null;
        counter = 0;
    }

}

But after I clear the contents in a file my "counter" not increasing. But my file is having some data. I think after reading done I have set my "myReader" to some intial..? If its how to set that to initial so that .readLine() should start from beginin开发者_如何学Gog.

• Shouldn't you close myReader before writing to the file??

LineNumberReader myReader = new LineNumberReader( new FileReader(new File("mnt/sdcard/abc.txt")));
while(true)
{   
    while(myReader.readLine() != null) {
        counter++;
    }

    if(counter > 100 )
    {
        //CLOSE myReader
        myReader.close();
        PrintWriter writer = new PrintWriter("/mnt/sdcard/abc.txt");
        writer.print("");
        writer.close();
        writer = null;
        counter = 0;
        //REOPEN myReader
        myReader = new LineNumberReader( new FileReader(new File("mnt/sdcard/abc.txt")));
    }
}

• Shouldn't you make sure that changes to the file done by the server and changes to the file done by this loop are synchronized??

can you show how and where counter is declared and what other code might be modifying it? it is a matter of guessing without seeing that. meanwhile, maybe you can consider not reading the file content all the time and use the file size to determine if you should clean it.

long limit= .... //add your limit in bytes 
long fileSize = new File("mnt/sdcard/abc.txt").length();
if (fileSize > limit){
   //clean the file
} 

please also note to check what was mentioned in the other answers regarding closing the file or trying to clean it while it is open and the server is writing to it.

Issue a myReader.reset() after clearing the contents.