从 Java 文本文件中删除特定行？

Question

I want to delete a specific line from a text file. I found that line, but what to do next? Any idea?

Answer 1

There is no magic to removing lines.

• Copy the file line by line, without the line you don't want.
• Delete the original file.
• rename the copy as the original file.

Answer 2

Read file from stream and write it to another stream and skip the line which you want to delete

Answer 3

Try to read file:

 public static String readAllText(String filename) throws Exception {
    StringBuilder sb = new StringBuilder();
    Files.lines(Paths.get(filename)).forEach(sb::append);
    return sb.toString();
}

then split text from specific character (for new line "\n")

private String changeFile(){
String file = readAllText("file1.txt"); 
String[] arr = file.split("\n"); // every arr items is a line now.
StringBuilder sb = new StringBuilder();
for(String s : arr)
{
   if(s.contains("characterfromlinewillbedeleted"))
   continue;
   sb.append(s); //If you want to split with new lines you can use sb.append(s + "\n");
}
return sb.toString(); //new file that does not contains that lines.
}

then write this file's string to new file with:

public static void writeAllText(String text, String fileout) {
    try {
        PrintWriter pw = new PrintWriter(fileout);
        pw.print(text);
        pw.close();
    } catch (Exception e) {
        //handle exception here
    }
}


writeAllText(changeFile(),"newfilename.txt");

Answer 4

Try this code.

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;


class Solution {
    public static void main(String[] args) throws FileNotFoundException, IOException{

        File inputFile = new File("myFile.txt");
        File tempFile = new File("myTempFile.txt");

        BufferedReader reader = new BufferedReader(new FileReader(inputFile));
        BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));

        String lineToRemove = "bbb";
        String currentLine;

        while((currentLine = reader.readLine()) != null) {
            // trim newline when comparing with lineToRemove
            String trimmedLine = currentLine.trim();
            if(trimmedLine.equals(lineToRemove)) continue;
            writer.write(currentLine + System.getProperty("line.separator"));
        }
        writer.close(); 
        reader.close(); 
        boolean successful = tempFile.renameTo(inputFile);
        System.out.println(successful);

    }
}

Answer 5

Deleting a text line directly in a file is not possible. We have to read the file into memory, remove the text line and rewrite the edited content.

Answer 6

Maybe a search method would do what you want ie "search" method takes a string as a parameter and search for it into the file and replace the line contains that string.

PS:

public static void search (String s)
{
    String buffer = "";
    try {

        Scanner scan = new Scanner (new File ("filename.txt"));
        while (scan.hasNext())
        {
            buffer = scan.nextLine();

            String [] splittedLine = buffer.split(" ");
            if (splittedLine[0].equals(s))
            {

                buffer = "";

            }
            else
            {
                //print some message that tells you that the string not found


            }
        }
        scan.close();

    } catch (FileNotFoundException e) {
        System.out.println("An error occured while searching in file!");
    }

}