Question

I have content of a file in a StringBuffer. The content of the file includes many lines (not on a single line). I want to edit the content of a line from index 4 (just for example) to the end of that line. I use replace() to edit the content of the StringBuffer.

The point is that the replace method has parameters such as starting index and ending index. But I don’t know what is the ending index since each line have different number of characters

I think of using str.indexOf("\n") to find the ending index of the line, but then the file have many lines, so it will return incorrect results.

this is the readFile() if u need to read the code

Thank you

public StringBuffer readFile(){ //read file line by line
    File f = getFilePath(fileName);
    StringBuffer sb = new StringBuffer();
    String textinLine;

    try {
        FileInputStream fs = new FileInputStream(f);
        InputStreamReader in = new InputStreamReader(fs);
        BufferedReader br = new BufferedReader(in);

     while (true){
            textinLine = br.readLine();
            if (textinLine == null) break;
            sb.append(textinLine+ "\n");
        }
        fs.close();
        in.close();
        br.close();
    } ... // just some catch statements heres
}

Answer 1

Use String.indexOf() as you indicated, but pass in the starting position, e.g. indexOf('\n', 4);