How to replace a specific line in a file using Java?
11,637
If you are using Java 7 or higher and if lineNumber
starts in 1, you can do the following:
public static void setVariable(int lineNumber, String data) throws IOException {
Path path = Paths.get("data.txt");
List<String> lines = Files.readAllLines(path, StandardCharsets.UTF_8);
lines.set(lineNumber - 1, data);
Files.write(path, lines, StandardCharsets.UTF_8);
}
Obviously if lineNumber
starts in 0, then:
lines.set(lineNumber, data);
Author by
Admin
Updated on July 22, 2022Comments
-
Admin almost 2 years
How do I write over a specific line in a text file using FileWriter and PrintWriter? I don't want to have to make a new file every time.
Edit: Can I just cycle through the file, get the length of the String at the indicated line number, and then use that length to backspace once I get to that line (to delete the String), and write in the new data?
public static void setVariable(int lineNumber, String data) { try { // Creates FileWriter. Append is on. FileWriter fw = new FileWriter("data.txt", true); PrintWriter pw = new PrintWriter(fw); //cycles through file until line designated to be rewritten is reached for (int i = 1; i <= lineNumber; i++) { //TODO: need to figure out how to change the append to false to overwrite data if (i == lineNumber) { pw.println(data); pw.close(); } else { // moves printwriter focus to next line (doesn't overwrite) pw.println(""); } } } }