Java - BufferedReader Class

---

---

Introduction

The Java BufferedReader class reads text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines.Following are the important points about BufferedReader −

• The buffer size may be specified, or the default size may be used.

• Each read request made of a Reader causes a corresponding read request to be made of the underlying character or byte stream.

Class declaration

Following is the declaration for Java.io.BufferedReader class −

public class BufferedReader
   extends Reader

Field

Following are the fields for Java.io.BufferedReader class −

• protected Object lock − This is the object used to synchronize operations on this stream.

Class constructors

Class methods

Methods inherited

This class inherits methods from the following classes −

• Java.io.Reader
• Java.io.Object

Example - Using mark() and reset() for Re-reading a Portion of the Input

The following example shows the usage of Java BufferedReader mark() and reset() methods.

BufferedReaderDemo.java

package com.tutorialspoint;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.StringReader;

public class BufferedReaderDemo {
   public static void main(String[] args) {
      // Input string
      String input = "Hello, World!\nThis is a BufferedReader example.\nHave a nice day!";

      try (BufferedReader reader = new BufferedReader(new StringReader(input))) {
         // Read the first line
         System.out.println(reader.readLine());

         // Mark the current position in the stream
         reader.mark(100); // Allows reading up to 100 characters before the mark is invalid

         // Read the next line
         System.out.println(reader.readLine());

         // Reset the reader to the marked position
         reader.reset();

         // Re-read the line after reset
         System.out.println(reader.readLine());
      } catch (IOException e) {
         System.err.println("An error occurred: " + e.getMessage());
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Hello, World!
This is a BufferedReader example.
This is a BufferedReader example.

Explanation

• A BufferedReader is initialized with a StringReader that wraps the input string.

• The first line is read using readLine() method.

• The mark(100) method marks the current position, allowing up to 100 characters to be read before the mark becomes invalid.

• After reading another line, the reset() method is called to return the reader to the marked position.

• The previously read line is re-read after the reset.

Example - Reading and Printing Each Character

The following example shows the usage of Java BufferedReader read() method.

BufferedReaderDemo.java

package com.tutorialspoint;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.StringReader;

public class BufferedReaderDemo {
   public static void main(String[] args) {
      String input = "Hello, World!";

      // Initialize BufferedReader with a StringReader
      try (BufferedReader reader = new BufferedReader(new StringReader(input))) {
         int character;

         System.out.println("Reading characters one by one:");

         // Read each character until the end of the stream
         while ((character = reader.read()) != -1) {
            // Print the character (cast the integer to char)
            System.out.print((char) character);
         }
      } catch (IOException e) {
         System.err.println("An error occurred: " + e.getMessage());
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Reading characters one by one:
Hello, World!

Explanation

• A BufferedReader is initialized with a StringReader containing the string "Hello, World!".

• The read() method reads one character at a time from the stream.

• The returned integer is cast to a char to display the actual character.

• The loop continues until the end of the stream is reached (read() returns -1).

Example - Skipping Characters and Reading the Remaining Input

The following example shows the usage of BufferedReader skip(long n) method.

BufferedReaderDemo.java

package com.tutorialspoint;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.StringReader;

public class BufferedReaderDemo {
   public static void main(String[] args) {
      String input = "Hello, World! This is a BufferedReader skip() example.";

      // Initialize BufferedReader with a StringReader
      try (BufferedReader reader = new BufferedReader(new StringReader(input))) {
         // Skip the first 7 characters
         long skipped = reader.skip(7);
         System.out.println("Skipped characters: " + skipped);

         // Read and print the remaining input
         String remaining = reader.readLine();
         System.out.println("Remaining input: " + remaining);
      } catch (IOException e) {
         System.err.println("An error occurred: " + e.getMessage());
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Skipped characters: 7
Remaining input: World! This is a BufferedReader skip() example.

Explanation

• The BufferedReader is initialized with a string containing a sentence.

• The skip(7) method skips the first 7 characters in the stream ("Hello, ").

• The program prints the number of characters actually skipped.

• The readLine() method reads and prints the remaining input.