CODEWITHSUNDEEP
java
Abszol
Abszol

Reputation: 57

Writing to specified line in Java?

To clarify my question, I am writing to a text file located on my computer which has text content already in it. The code below writes to the text file without erasing any of its contents but now I want to specify what line it writes to. Currently it has an if statement to catch if the word 'Done' exists within in the line, it is recognized since it does write to the file. My problem is trying to get it to write to the line that says 'Done'. It writes to the very bottom, last line of code. How can I fix this?

The method readNumLines is the number of lines contained within the file. Reading is the text file name.

int i = 0;
    BufferedReader reader = new BufferedReader(new FileReader(path+reading));
    BufferedWriter writer = new BufferedWriter(new FileWriter(path+reading, true));
    String line = null;
    while ((line = reader.readLine()) != null && i < readNumLines(reading)-1) {
        if(line.contains("Done")){
            writer.write("\nCHECK!\n");
            writer.close();
        }
        i++;
    }

Upvotes: 0

Views: 3026

Answers (3)

ifloop
ifloop

Reputation: 8386

When using Java 8, you might try this:

final Path myFile = Paths.get("path\\to\\yourFile.txt");
final int lineNumWhereToInsert = 2;
final String stringToInsert = "insertion test";

try {
    final List<String> lines = Files.lines(myFile).collect(Collectors.toList());
    lines.add(Math.min(lineNumWhereToInsert, lines.size()), stringToInsert);

    try (final BufferedWriter out = Files.newBufferedWriter(myFile, Charset.forName("UTF-8"))) {
        for (final String line : lines) {
            out.append(line).append(System.lineSeparator());
        }
    }
} catch (IOException) {
    ex.printStrackTrace();
}

Upvotes: 0

Roan
Roan

Reputation: 1206

This is my way of doing it.The idea is simple write everything including the new line to a temp file and then rename the temp file to the Original file and delete the orginal one. NOTE: I pulled this code staigt from one of my project and therefore I may have forgotten to change something. So if it doesn't work let me know and I will have a look. Hope this helps :)

            String line;//You need to specify those
            File infile;

            // temp file
            File outFile = new File("$$$$$$$$.tmp");

            // input
            FileInputStream fis = null;
            try {
                fis = new FileInputStream(inFile);
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
            BufferedReader in = new BufferedReader(new InputStreamReader(fis));

            // output         
            FileOutputStream fos = null;
            try {
                fos = new FileOutputStream(outFile);
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
            PrintWriter out = new PrintWriter(fos);
            String thisLine = "";
            int i =1;
            try {
                while ((thisLine = in.readLine()) != null) {
                   if(in.contains("Done"))//the check for done 
                       out.println(line);                  
                   }
                   out.println(thisLine);
                   i++;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
            out.flush();
            out.close();
            try {
                in.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            inFile.delete();
            outFile.renameTo(inFile);

Upvotes: 0

Alex
Alex

Reputation: 68

I suggest reading the whole file into a variable (string, array or list). You can easily modify specific lines then and write everything back to the file.

1) Reading File into an array: Store text file content line by line into array

2) Manipulate array:

for (int i = 0; i < lines.length; i++) {
            String line = lines[i];
            if (line.contains("Done")) {
                lines[i] = line + "\nCHECK!\n";
                break;
            }
}

3) Write string array to file: Writing a string array to file using Java - separate lines

The problem also can be related to this line:

writer.write("\nCHECK!\n");

the first "\n" forces the "CHECK" to be written in a new line. This assumes that your "Done" line is the last line and does not end with "\n".

Upvotes: 1

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