Remove a specific line in a file using line number

Question

So the problem is I have a text file storing information that has many lines. Each line should look like this:

Product :< name: , Importing Price: , quantity: >

I'm trying to write code that helps the users to input a number and the program will find a line corresponding to that number and remove that line. Any suggestions?

Read this: http://stackoverflow.com/questions/20039980/java-replace-line-in-text-file — T D Nguyen, Apr 08 '16 at 05:07
Read this [How to read a specific line using the specific line number from a file in Java?](http://stackoverflow.com/questions/2312756/how-to-read-a-specific-line-using-the-specific-line-number-from-a-file-in-java) — Braj, Apr 08 '16 at 05:20
Is it a file that contains fixed length of chars in each line then easily you can jump to specific line number without reading previous ones otherwise you have read all previous lines and keep count on read line numbers. Use [RandomAccessFile](https://docs.oracle.com/javase/7/docs/api/java/io/RandomAccessFile.html) or [LineNumberReader](https://docs.oracle.com/javase/7/docs/api/java/io/LineNumberReader.html) or [BufferedReader](https://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html) — Braj, Apr 08 '16 at 05:21

score 1 · Answer 1 · answered Apr 08 '16 at 05:26

1

Try to use to below line of code :

FileInputStream fs= new FileInputStream("someFile.txt");

BufferedReader reader = new BufferedReader(new InputStreamReader(fs));
BufferedWriter writer = new BufferedWriter(new FileWriter(fs));

for(int i = 0; i < file_length; ++i){
   br.readLine();
   String lineIWant = br.readLine();
   if(i==your line number){
       i = file_length;
       writer.write(currentLine + System.getProperty("line.separator"));
   }
}
reader.close();
writer.close();

answered Apr 08 '16 at 05:26

Bhunnu Baba

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How will you get ``file_length`` ? – muzahidbechara Apr 09 '16 at 14:34
@muzahidbechara plz read this link http://stackoverflow.com/questions/12749655/how-to-count-lines-in-file-txt-android – Bhunnu Baba Apr 11 '16 at 06:33
Why is your code so messy?.. `if(i==your line number){ //error`, `br.readLine();` - `br` doesn't exists, it's about `reader` variable. Better include complete code that we can compile – Frankie Drake May 25 '18 at 12:33

score 0 · Answer 2 · answered Apr 08 '16 at 05:50

You can also use LineNumberReader:

import java.io.LineNumberReader;
import java.io.FileReader;
import java.io.IOException;

class Stackoverflow36491903 {
    public static void main(String[] args) throws IOException {
        int lineNo = Integer.valueOf(args[1]);

        LineNumberReader r = new LineNumberReader(new FileReader(args[0]));
        while (true) {
            String line = r.readLine();
            if (line == null) {
                break;
            }
            if (r.getLineNumber() != lineNo) {
                System.out.println(line);
            }
        }
    }
}

Takes two arguments: name of the file, and a line number.

This just prints the lines removing the line at the requested line number.

Use a writer to write it back to a file.

score 0 · Answer 3 · answered Apr 08 '16 at 06:03

Scanner scan = new Scanner(System.in);
int lineNum = scan.nextInt();
File file = new File("file.txt");
FileReader reader = new FileReader(file);
scan = new Scanner(reader);
StringBuilder sb = new StringBuilder("");
while(scan.hasNextLine()) {
    String line = scan.nextLine();
    if (--lineNum != 0) sb.append(line).append(System.getProperty("line.separator"));
}
FileWriter writter = new FileWriter(file);
writter.write(sb.toString());

Remove a specific line in a file using line number

3 Answers3