CODEWITHSUNDEEP
javatext-filesreadfile
user7575308
user7575308

Reputation: 81

Read BIG txt file with metod JAVA

Hello I have a problem with read file.

I have BIG .txt file (500MB)

And I want read line with method I start method medhor rsault is first line. I start method second and return second line

I have this code. I save last read line and read line+1 but program stoped in each line < last read line. and if I read 100 000< line it's too long. 

public  static Boolean Jedno(){
        int poradievtahu=0;
        int[] tah=new int[7];
        String subor= "C:/Users/Paradox/workspace/Citaj_po_Riadku/all6.txt";
        Scanner sc;
        try {
            sc = new Scanner(new File(subor));
            int lineIndex = 0;
    cit:    while(sc.hasNextLine()) {
            String line = sc.nextLine();
            if(lineIndex++ >= pocetC+1) {
                System.out.print("Zvacsujem "+ (pocetC+1) + " " + line);
                // do something
                poradievtahu=-1;
                Scanner scanner=new Scanner(line);
                        while(scanner.hasNextInt()){
                           int pom= scanner.nextInt();

                          tah[++poradievtahu]=pom;
                           if (poradievtahu==5){
                               poradievtahu=-1;
                               pocetC++;

                               if ((pocetC%(55935)==0)&&(pocetC!=0)){
                                  Calendar cal = Calendar.getInstance();
                                 PrintWriter writer4 = new PrintWriter(new BufferedWriter(new FileWriter("nove.txt", true)));
                                    SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
                                    writer4.println("Ďalšia 1/1470  in " + sdf.format(cal.getTime()));
                                    writer4.println(Arrays.toString(tah));
                                    writer4.close();
                               }
                              if (pocetC>=13983816){
                                   //berem=false;                                   
                                   PrintWriter writer4 = new PrintWriter(new BufferedWriter(new FileWriter("mozne.txt", true)));
                                    Calendar cal = Calendar.getInstance();
                                   SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
                                    writer4.println("End file in " + sdf.format(cal.getTime()));                                    
                                    writer4.close();    

                                    return true;
                               }

                              Pocty.hladam=tah;
                           }
                        }
                break cit;
            }
        }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return false;
    }

Please have you some ides how resolve problem? BUT if I set line 500 000 it's over 1 s. but file have 19 000 000 lines..

Upvotes: 0

Views: 282

Answers (1)

Daler.Dixus
Daler.Dixus

Reputation: 54

I am not sure whether I got your idea, but if you want to process some lines in file starting from line X to line Y, I would recommend using File.lines() method:

public static void processLinesFromPoint(int startLine, int numberOfLinesToProcess) throws IOException {
    //assume startLine = 5000
    //       numberOfLinesToProcess = 500
    Stream<String> lines = Files.lines(Paths.get(pathToYourFile)).skip(startLine).limit(numberOfLinesToProcess);
    //lines.forEach method to loop through lines 5000 to 5500  (startLine+numberOfLinesToProcess)
    //and printing each line
    lines.forEach(currentLine->{
        //here goes your logic to process each line...
        System.out.println(currentLine)
    });
}

Files.lines has functions so you can get required amount of lines and use Files.lines().count() to get total lines in file.

P.S: I use this method to process files over 2Gb, I hope the answer will be useful)

Upvotes: 4

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