What is BufferedReader in Java
In Java, BufferedReader is a class that is part of the java.io package. It is used for reading text from a character-based input stream efficiently by buffering the characters. The primary purpose of using a BufferedReader is to improve the performance of reading data from an input stream by reducing the number of I/O operations.
Here's a simple explanation of how BufferedReader works:
1. Buffering: Instead of reading one character at a time from the underlying input stream, BufferedReader reads a chunk of characters (a buffer) into memory. This helps reduce the number of reads from the underlying stream and improves overall performance.
2. Read Methods: BufferedReader provides various methods for reading characters, lines, or other data types from the input stream. Some common methods include read(), readLine(), and read(char[] cbuf, int off, int len).
3. Closing: It's important to note that when you are done using a BufferedReader, you should close it using the close() method to release system resources.
Here's a simple example of using BufferedReader to read lines from a file:
import java.io.BufferedReader;import java.io.FileReader;import java.io.IOException;public class Example {public static void main(String[] args) {// Specify the path of the file to be readString filePath = "path/to/your/file.txt";try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {String line;while ((line = reader.readLine()) != null) {System.out.println(line);}} catch (IOException e) {e.printStackTrace();}}}
In this example, BufferedReader is used to read lines from a file (file.txt). The readLine() method reads a line of text, and the process continues until the end of the file is reached (when readLine() returns null). The try-with-resources statement is used to automatically close the BufferedReader after use.
Why we need to use BufferedReader in Java
BufferedReader in Java is used for efficient reading of characters from a Reader (like FileReader or InputStreamReader). It provides buffering, which means it reads data from a file, input stream, or other source into an internal buffer and then reads from that buffer, rather than directly from the source. This can lead to improved performance when reading large amounts of data.
Here are some reasons why BufferedReader is commonly used in Java:
1. Improved Performance: Reading data from a file or an input stream involves I/O operations, which can be relatively slow. By using a buffer, you can minimize the number of actual I/O operations, making the overall process more efficient.
2. Reading Line by Line: BufferedReader provides a convenient method, readLine(), which allows you to read a line of text at a time. This is useful when dealing with text files where data is organized into lines.
BufferedReader reader = new BufferedReader(new FileReader("example.txt"));String line = reader.readLine();while (line != null) {// Process the lineSystem.out.println(line);line = reader.readLine();}reader.close();
3. Efficient Character Reading: It allows for efficient reading of characters, thanks to buffering. This is particularly beneficial when dealing with large files or streams.
BufferedReader reader = new BufferedReader(new FileReader("largeFile.txt"));int character;while ((character = reader.read()) != -1) {// Process the characterSystem.out.print((char) character);}reader.close();
4. Mark and Reset: BufferedReader supports the mark(int readAheadLimit) and reset() methods, which allow you to mark a position in the input stream and later reset back to that position. This can be useful in certain scenarios.
BufferedReader reader = new BufferedReader(new FileReader("example.txt"));reader.mark(100); // Marking the current position// Read and process some datareader.reset(); // Resetting back to the marked position// Continue reading from the marked position
In summary, BufferedReader is commonly used in Java for efficient, buffered reading of characters from various sources, providing better performance and convenient methods for handling text data.
How BufferedReader Works Internally?
In Java, BufferedReader is a class that is part of the java.io package and is used for reading text from a character-based input stream with efficient buffering. It provides methods for reading lines, characters, and other data from a source such as a file or an input stream. Here's a brief overview of how BufferedReader works internally:
1. Constructor:
When you create a BufferedReader, you typically pass an instance of another Reader (e.g., FileReader, StringReader) to its constructor. This underlying Reader is used to read data from the source.
Reader reader = new FileReader("example.txt");BufferedReader bufferedReader = new BufferedReader(reader);
2. Buffering:
BufferedReader uses an internal buffer to store a chunk of data read from the underlying Reader. This helps in reducing the number of actual reads from the source, making the reading process more efficient.
int defaultCharBufferSize = 8192;char[] cb = new char[defaultCharBufferSize];
The default buffer size is 8192 characters, but you can specify a different size if needed.
3. Reading:
When you call read() or readLine() on a BufferedReader, it checks whether there is data available in the buffer. If the buffer is empty or does not contain the required number of characters, it reads a chunk of data from the underlying Reader into the buffer.
int n;while ((n = in.read(cb, 0, cb.length)) != -1) {// Process the characters in the buffer}
The read() method returns the number of characters read into the buffer, or -1 if there is no more data.
4. Line Reading:
BufferedReader provides a convenient readLine() method to read a line of text. It reads characters from the buffer until it encounters a newline character ('\n') or reaches the end of the stream.
String line = bufferedReader.readLine();
5. Closing:
When you call the close() method on a BufferedReader, it also closes the underlying Reader. This ensures that system resources are released properly.
bufferedReader.close();
In summary, BufferedReader works by efficiently reading and buffering data from an underlying Reader, which may be a file, an input stream, or any other character-based data source. This buffering helps to minimize the number of actual reads from the source, improving overall performance.
When to use BufferedReader in Java
BufferedReader in Java is used to read text from a character-based input stream efficiently by buffering the characters. It provides a more efficient way to read characters, lines, or other data from a file or an input stream compared to reading directly from the underlying stream. Here are some scenarios where you might want to use BufferedReader:
1. Reading Text Files Efficiently:
When reading text from a file in Java, using BufferedReader can be more efficient than reading directly from a FileReader. The buffering mechanism helps reduce the number of I/O operations, making the process faster.
try (BufferedReader reader = new BufferedReader(new FileReader("example.txt"))) {String line;while ((line = reader.readLine()) != null) {// Process each line}} catch (IOException e) {e.printStackTrace();}
2. Reading Input from InputStreamReader:
When reading text from an InputStreamReader, which is commonly used for reading from standard input or network streams, using BufferedReader can improve performance.
try (BufferedReader reader = new BufferedReader(new InputStreamReader(System.in))) {String userInput = reader.readLine();// Process the user input} catch (IOException e) {e.printStackTrace();}
3. Parsing and Tokenizing:
When you need to parse or tokenize input, BufferedReader can be useful in reading lines and then processing them as needed.
try (BufferedReader reader = new BufferedReader(new FileReader("data.csv"))) {String line;while ((line = reader.readLine()) != null) {String[] tokens = line.split(",");// Process tokens}} catch (IOException e) {e.printStackTrace();}
4. Reading Data from Network Streams:
When working with network streams, using BufferedReader can be beneficial for reading data efficiently.
try (Socket socket = new Socket("example.com", 8080);BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()))) {String response;while ((response = reader.readLine()) != null) {// Process the response from the server}} catch (IOException e) {e.printStackTrace();}
In general, BufferedReader is a good choice whenever you need to read data from a character-based input source in a buffered manner, providing better performance compared to unbuffered alternatives.