Java - CharArrayReader Class

---

---

Introduction

The Java CharArrayReader class implements a character buffer that can be used as a character-input stream.

Class declaration

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

 public class CharArrayReader extends Reader 

Field

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

• protected char[] buf − This is the character buffer.

• protected int count − This is the index of the end of this buffer.

• protected int markedPos − This is the position of mark in buffer.

• protected int pos − This is the current buffer position.

• 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 - Closing the Stream After Use

The following example shows the usage of Java CharArrayReader close() method.

CharArrayReaderDemo.java

 package com.tutorialspoint; import java.io.CharArrayReader; import java.io.IOException; public class CharArrayReaderDemo { public static void main(String[] args) { char[] data = "Hello, World!".toCharArray(); // Create a CharArrayReader CharArrayReader reader = new CharArrayReader(data); try { // Read and print characters System.out.println("Reading characters:"); int charData; while ((charData = reader.read()) != -1) { System.out.print((char) charData); } // Close the reader reader.close(); System.out.println("\nCharArrayReader closed."); } catch (IOException e) { System.err.println("An IOException occurred: " + e.getMessage()); } } } 

Output

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

 Reading characters: Hello, World! CharArrayReader closed. 

Explanation

• A CharArrayReader is created using a character array containing "Hello, World!".

• Characters are read and printed one by one until the end of the stream.

• The close() method is called to formally close the reader after use.

• Since CharArrayReader doesn't use external resources, closing is optional but recommended for consistency.

Example - Basic Use of mark(int readAheadLimit)

The following example shows the usage of Java CharArrayReader mark(readAheadLimit) method.

CharArrayReaderDemo.java

 package com.tutorialspoint; import java.io.CharArrayReader; import java.io.IOException; public class CharArrayReaderDemo { public static void main(String[] args) { char[] data = "Hello, World!".toCharArray(); // Create a CharArrayReader CharArrayReader reader = new CharArrayReader(data); try { // Read and print the first three characters System.out.print("Initial characters: "); for (int i = 0; i < 3; i++) { System.out.print((char) reader.read()); } System.out.println(); // Mark the current position reader.mark(0); // The readAheadLimit is ignored in CharArrayReader System.out.println("Marked current position."); // Read and print the next three characters System.out.print("Next characters: "); for (int i = 0; i < 3; i++) { System.out.print((char) reader.read()); } System.out.println(); // Reset the stream to the marked position reader.reset(); System.out.println("Stream reset to the marked position."); // Read and print the same three characters again System.out.print("Characters after reset: "); for (int i = 0; i < 3; i++) { System.out.print((char) reader.read()); } System.out.println(); } catch (IOException e) { System.err.println("IOException occurred: " + e.getMessage()); } } } 

Output

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

 Initial characters: Hel Marked current position. Next characters: lo, Stream reset to the marked position. Characters after reset: lo, 

Explanation

• The first three characters (Hel) are read and printed.

• The mark() method is called to mark the current position after reading three characters.

• After reading the next three characters (lo,), the reset() method is called to return the stream to the marked position.

• The same three characters (lo,) are read again after the reset.

Example - Simple Check for markSupported()

The following example shows the usage of Java CharArrayReader mark(readAheadLimit) method.

CharArrayReaderDemo.java

 package com.tutorialspoint; import java.io.CharArrayReader; public class CharArrayReaderDemo { public static void main(String[] args) { char[] data = "Hello, World!".toCharArray(); // Create a CharArrayReader CharArrayReader reader = new CharArrayReader(data); // Check if mark is supported if (reader.markSupported()) { System.out.println("Mark and reset are supported by CharArrayReader."); } else { System.out.println("Mark and reset are NOT supported by CharArrayReader."); } } } 

Output

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

 Mark and reset are supported by CharArrayReader. 

Explanation

• A CharArrayReader is created using a character array containing "Hello, World!".

• The markSupported() method is called to check if the mark() and reset() methods are supported.

• Since CharArrayReader always supports marking, the output will confirm that "Mark and reset are supported by CharArrayReader."