Java BufferedWriter

BufferedWriter

The BufferedWriter class is used to write text to a file, one line or one string at a time. If the file already exists, its contents will be replaced (overwritten).

Write to a Text File

Use BufferedWriter with FileWriter to write text to a file. The write() method adds text, and you can use newLine() to insert a line break:

Example

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class Main {
  public static void main(String[] args) {
    try (BufferedWriter bw = new BufferedWriter(new FileWriter("filename.txt"))) {
      bw.write("First line");
      bw.newLine();  // add line break
      bw.write("Second line");
      System.out.println("Successfully wrote to the file.");
    } catch (IOException e) {
      System.out.println("Error writing file.");
    }
  }
}

Explanation: This program creates (or overwrites) filename.txt and writes two lines of text into it. The newLine() method inserts a line break between "First line" and "Second line". If everything goes well, the console will print "Successfully wrote to the file."

Append to a Text File

To add new content to the end of a file (instead of overwriting), pass true to FileWriter:

Example

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class Main {
  public static void main(String[] args) {
    // true = append mode
    try (BufferedWriter bw = new BufferedWriter(new FileWriter("filename.txt", true))) {
      bw.newLine();                      // move to a new line
      bw.write("Appended line");         // add new text at the end
      System.out.println("Successfully appended to the file.");
    } catch (IOException e) {
      System.out.println("Error writing file.");
    }
  }
}

Explanation: This program keeps the existing content of filename.txt and adds a new line with the text "Appended line" at the end. If everything works, the console prints "Successfully appended to the file."

Comparing File Writing Classes

Java gives you several ways to write to files. Here's when to pick each one:

• FileWriter - best for simple text writing. Quick and easy to use.
• BufferedWriter - better for larger text files, because it is faster and lets you easily add line breaks with newLine().
• FileOutputStream - best for binary files (like images, PDFs, or audio)