Question

I have a log package.I want to filter the log.e, and save it to another file. But I find BufferedWriter can not reach the expected effect. Such as the two lines in log file below can not store another file.

E/Vold ( 96): Sleep 2s to make sure that coldboot() events are handled
E/WindowManager( 244): setEventDispatching false

attach code:

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class LogSpider {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub

        BufferedReader bufferedReader = null;

        try {
            bufferedReader = new BufferedReader(new FileReader("C:\\Users\\Administrator\\Desktop\\log.txt"));
            String line = "";

            try {
                while((line = bufferedReader.readLine())!=null)
                {
                    Parseelog(line);
                }
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        finally{
            try {
                bufferedReader.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

    public static void Parseelog(String line)
    {
        BufferedWriter bufferedWriter = null;        
        try {
            bufferedWriter = new BufferedWriter(new FileWriter("C:\\Users\\Administrator\\Desktop\\logspider2.txt"));
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

        //Pattern pattern = Pattern.compile("[\\w[.-]]+\\@[\\w[.-]]{2,}\\.[\\w[.-]]+");
        Pattern pattern = Pattern.compile("^E.*");
        Matcher matcher = pattern.matcher(line);

        while(matcher.find())
        {
            String string = new String(matcher.group());
            string += "\n";

            System.out.println(string); //here can print the search results 

            try {
                bufferedWriter.write(string, 0, string.length());
                bufferedWriter.flush();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }    

            finally{
                try {
                    bufferedWriter.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }    
        }
    }

}

Answer 1

The problem with you code was that you where opening the logspider2.txt file every time you want to write the matching line. So it was overwriting all the previous data. To solve the issue you need to open your file in the append mode as follows:

bufferedWriter = new BufferedWriter(
                    new FileWriter(
                            "F:\\praful\\androidworkspace_2\\Test\\src\\logspider2.txt",true));

I tried you code and made some modification to make it work. Following is the working code:

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub

        BufferedReader bufferedReader = null;

        try {
            bufferedReader = new BufferedReader(new FileReader(
                    "F:\\praful\\androidworkspace_2\\Test\\src\\logs.txt"));
            String line = "";

            try {
                while ((line = bufferedReader.readLine()) != null) {
                    Parseelog(line);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            try {
                bufferedReader.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

    public static void Parseelog(String line) {
        BufferedWriter bufferedWriter = null;
        // Pattern pattern =
        // Pattern.compile("[\\w[.-]]+\\@[\\w[.-]]{2,}\\.[\\w[.-]]+");
        Pattern pattern = Pattern.compile("^E.*");
        Matcher matcher = pattern.matcher(line);

        try {
            bufferedWriter = new BufferedWriter(
                    new FileWriter(
                            "F:\\praful\\androidworkspace_2\\Test\\src\\logspider2.txt",true));

            while (matcher.find()) {
                String string = new String(matcher.group());
                string += "\n";

                System.out.println(string); // here can print the search results

                bufferedWriter.write(string);

            }

            bufferedWriter.flush();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                bufferedWriter.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }

}

Please changed the file path to your local paths. Hope it help you..