Java BufferedWriter
Efficient text writing with buffering capabilities
✍️ What is BufferedWriter?
BufferedWriter writes text efficiently by buffering characters in memory before writing to files. It's ideal for writing large amounts of text with improved performance.
// Basic BufferedWriter example
import java.io.*;
BufferedWriter bw = new BufferedWriter(new FileWriter("output.txt"));
bw.write("Hello World!");
bw.close();
Result:
Creates 'output.txt' with "Hello World!"
BufferedWriter Features
Text Writing
Write text files efficiently
bw.write("Hello World!");Buffered Output
Faster writing with buffer
BufferedWriter bw = new BufferedWriter(writer);Line Writing
Write lines with newlines
bw.newLine();Force Write
Flush buffer to disk
bw.flush();🔹 Basic BufferedWriter Usage
Here's how to write to a text file using BufferedWriter:
import java.io.*;
public class BufferedWriterExample {
public static void main(String[] args) {
try {
// Create BufferedWriter
FileWriter fw = new FileWriter("report.txt");
BufferedWriter bw = new BufferedWriter(fw);
// Write content
bw.write("Daily Report");
bw.newLine();
bw.write("=============");
bw.newLine();
bw.write("Tasks completed: 5");
bw.newLine();
bw.write("Status: Success");
// Close the writer
bw.close();
System.out.println("Report written successfully!");
} catch (IOException e) {
System.out.println("Error: " + e.getMessage());
}
}
}Output:
Report written successfully!
File 'report.txt' contains formatted report
🔹 Try-with-Resources
Modern approach with automatic resource management:
import java.io.*;
public class ModernBufferedWriter {
public static void main(String[] args) {
// Automatic resource management
try (BufferedWriter bw = new BufferedWriter(new FileWriter("notes.txt"))) {
// Write multiple lines
String[] notes = {
"Java I/O is powerful",
"BufferedWriter improves performance",
"Always close your streams",
"Try-with-resources is recommended"
};
for (String note : notes) {
bw.write("• " + note);
bw.newLine();
}
System.out.println("Notes saved successfully!");
} catch (IOException e) {
System.out.println("Writing error: " + e.getMessage());
}
// BufferedWriter is automatically closed
}
}Output:
Notes saved successfully!
File contains bulleted list of notes
🔹 Append Mode
Add content to existing files without overwriting:
import java.io.*;
import java.time.LocalDateTime;
public class AppendExample {
public static void main(String[] args) {
try (BufferedWriter bw = new BufferedWriter(new FileWriter("log.txt", true))) {
// Add timestamp and log entry
String timestamp = LocalDateTime.now().toString();
bw.write("[" + timestamp + "] Application started");
bw.newLine();
bw.write("[" + timestamp + "] User logged in");
bw.newLine();
// Force write to disk
bw.flush();
System.out.println("Log entries added!");
} catch (IOException e) {
System.out.println("Logging error: " + e.getMessage());
}
}
}Output:
Log entries added!
Timestamped entries appended to 'log.txt'
🔹 Writing Large Data
BufferedWriter excels at writing large amounts of text:
import java.io.*;
public class LargeDataWriter {
public static void main(String[] args) {
try (BufferedWriter bw = new BufferedWriter(new FileWriter("data.csv"))) {
// Write CSV header
bw.write("ID,Name,Age,City");
bw.newLine();
// Write 1000 records
for (int i = 1; i <= 1000; i++) {
String record = i + ",User" + i + "," + (20 + i % 50) + ",City" + (i % 10);
bw.write(record);
bw.newLine();
// Flush every 100 records
if (i % 100 == 0) {
bw.flush();
System.out.println("Written " + i + " records...");
}
}
System.out.println("CSV file created successfully!");
} catch (IOException e) {
System.out.println("Error: " + e.getMessage());
}
}
}Output:
Written 100 records...
Written 200 records...
...
CSV file created successfully!
🔹 Custom Buffer Size
Optimize performance with custom buffer size:
import java.io.*;
public class CustomBufferWriter {
public static void main(String[] args) {
try {
// Create BufferedWriter with 16KB buffer
FileWriter fw = new FileWriter("bigfile.txt");
BufferedWriter bw = new BufferedWriter(fw, 16384);
// Write large content
for (int i = 0; i < 10000; i++) {
bw.write("This is line number " + i + " with some content.");
bw.newLine();
}
bw.close();
System.out.println("Large file written with custom buffer!");
} catch (IOException e) {
System.out.println("Error: " + e.getMessage());
}
}
}🔹 Common Methods
Important BufferedWriter methods:
- write(String s) - Writes a string
- write(char[] cbuf) - Writes character array
- write(int c) - Writes single character
- newLine() - Writes system line separator
- flush() - Forces write of buffered data
- close() - Closes the writer
// Method examples
BufferedWriter bw = new BufferedWriter(new FileWriter("example.txt"));
bw.write("Hello"); // Write string
bw.write(' '); // Write single character
bw.write("World!"); // Write another string
bw.newLine(); // Add line break
bw.flush(); // Force write to disk
bw.close(); // Always close!