删除其中带有特定字符串的一行文本

Question

I am trying to delete a text line from a file. So far I have this but it is giving me some problems. It works if there is nothing after the initial text on the line. But if in the text file I have anything after Bart ie Bart Jones for example, it will not delete the line, it will just leave it alone. Please help.

public void removeLineFromFile(String file, String lineToRemove) {

    try {

        File inFile = new File(file);

        if (!inFile.isFile()) {
            System.out.println("Parameter is not an existing file");
            return;
        }

        //Construct the new file that will later be renamed to the original filename.
        File tempFile = new File(inFile.getAbsolutePath() + ".tmp");

        BufferedReader br = new BufferedReader(new FileReader(file));
        PrintWriter pw = new PrintWriter(new FileWriter(tempFile));

        String line = null;

        //Read from the original file and write to the new
        //unless content matches data to be removed.
        while ((line = br.readLine()) != null) {

            if (!line.trim().equals(lineToRemove)) {

                pw.println(line);
                pw.flush();
            }
        }
        pw.close();
        br.close();

        //Delete the original file
        if (!inFile.delete()) {
            System.out.println("Could not delete file");
            return;
        }

        //Rename the new file to the filename the original file had.
        if (!tempFile.renameTo(inFile))
            System.out.println("Could not rename file");

    }
    catch (FileNotFoundException ex) {
        ex.printStackTrace();
    }
    catch (IOException ex) {
        ex.printStackTrace();
    }
}

public static void main(String[] args) {
    FileUtil util = new FileUtil();
    util.removeLineFromFile("booklist.txt", "bart");
}

} `

Answer 1

代替.equals(lineToRemove)使用.contains(lineToRemove)

Answer 2

Simply change

if (!line.trim().equals(lineToRemove))

with

if (!line.indexOf(lineToRemove) > -1)

• There is no need to trim as you only want to know if the string is in the line.
• indexOf generate less bytecode then contains as contains itself call indexOf with other trims.
• You might want to compare using toLowerCase if you don't matter of the case.

See Is String.Contains() faster than String.IndexOf()? for more info on comparing with indexOf vs contains .

Answer 3

You need to use not equals but contains in this line:

if (!line.trim().equals(lineToRemove)) {

Like this:

if (!line.contains(lineToRemove)) {

Answer 4

It has to do with the way you're searching for the string in the file. The goal is to delete a line "containing" a string, not "equals to" a string. Changing the if statement in the loop should do the trick.

 if (!line.trim().toLowerCase().contains(lineToRemove.toLowerCase())) {

            pw.println(line);
            pw.flush();
        }

Notice that I also added a call to toLowerCase() in case the search string and line content where in different cases, you'd probably want to delete them as well. If that's not the case, you can safely remove those calls.