Writing Files

Intermediate ~15 min read

Writing content to files is as important as reading. Java provides BufferedWriter and FileWriter for efficient text output.

Using BufferedWriter

Allows writing text to a character-output stream, buffering characters to provide for the efficient writing of single characters, arrays, and strings.

try (BufferedWriter bw = new BufferedWriter(new FileWriter("output.txt"))) {
    bw.write("Hello World");
    bw.newLine();
    bw.write("Java File I/O is great.");
} catch (IOException e) {
    e.printStackTrace();
}

Appending to a File

To append instead of overwrite, pass true to the FileWriter constructor:

new FileWriter("output.txt", true)

Full Example

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

public class IoWriting {
    public static void main(String[] args) {
        // Writing to a file (overwrites existing content)
        try {
            FileWriter writer = new FileWriter("output.txt");
            writer.write("Hello, World!\n");
            writer.write("This is a test file.\n");
            writer.write("Writing multiple lines.\n");
            writer.close();
            System.out.println("File written successfully!");
        } catch (IOException e) {
            System.out.println("Error writing file: " + e.getMessage());
        }
        
        // Appending to a file
        try {
            FileWriter writer = new FileWriter("output.txt", true);  // true = append mode
            writer.write("This line is appended.\n");
            writer.write("Another appended line.\n");
            writer.close();
            System.out.println("Content appended successfully!");
        } catch (IOException e) {
            System.out.println("Error appending to file: " + e.getMessage());
        }
    }
}

Output

Click Run to execute your code

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Using BufferedWriter

Appending to a File

Full Example

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