The Buffer class is an abstract class in the java.nio package, serving as the foundation for all buffer classes like ByteBuffer, CharBuffer, IntBuffer, etc. A buffer is a container for a fixed amount of data of a specific primitive type.
Commonly Used Methods
Simple Program using ByteBuffer
This program demonstrates basic usage of a buffer to store and retrieve bytes.
import java.nio.ByteBuffer;
public class SimpleBufferExample {
public static void main(String[] args) {
ByteBuffer buffer = ByteBuffer.allocate(10); // Capacity = 10
// Writing data to buffer
for (int i = 0; i < 5; i++) {
buffer.put((byte) (i + 65)); // storing ASCII A, B, C, D, E
}
buffer.flip(); // Switch from write mode to read mode
// Reading data from buffer
while (buffer.hasRemaining()) {
byte b = buffer.get();
System.out.println("Read: " + (char) b);
}
}
}Problem Statement:
LotusJavaPrince is building a lightweight logging framework. Mahesh suggests using CharBuffer to temporarily store log messages in memory before writing to a file. Write a Java program that stores log messages in a CharBuffer, marks specific positions (for rollback), and rewinds or resets if needed before writing to a file.
import java.io.FileWriter;
import java.io.IOException;
import java.nio.CharBuffer;
public class LogBufferSystem {
public static void main(String[] args) {
CharBuffer logBuffer = CharBuffer.allocate(100); // buffer with capacity of 100 chars
// Step 1: Write initial log messages
logBuffer.put("INFO: System Started\n");
logBuffer.put("DEBUG: Initializing modules\n");
logBuffer.mark(); // Marking this point
logBuffer.put("ERROR: Temporary glitch detected\n");
// Step 2: Reset back to mark if error should be ignored
logBuffer.reset(); // Rollback to marked point
logBuffer.put("INFO: System Running Smoothly\n");
// Prepare buffer for reading
logBuffer.flip();
// Step 3: Simulate writing to file
try (FileWriter fw = new FileWriter("logs.txt")) {
while (logBuffer.hasRemaining()) {
fw.write(logBuffer.get());
}
System.out.println("Logs written to logs.txt successfully.");
} catch (IOException e) {
e.printStackTrace();
}
}
}Output File (logs.txt):
INFO: System Started
DEBUG: Initializing modules
INFO: System Running SmoothlyCode language: HTTP (http)The Buffer class in Java NIO is a fundamental building block for handling data in a more efficient and flexible way compared to traditional I/O. It provides a container for a fixed amount of data and supports key properties such as capacity, limit, position, and mark to manage data read/write operations effectively.
As an abstract class, Buffer is extended by specific buffer types like ByteBuffer, CharBuffer, IntBuffer, etc., each designed to work with a particular primitive type. These buffers are essential when working with channels (FileChannel, SocketChannel, etc.), enabling non-blocking, buffered, and high-performance I/O.