Java - CharArrayReader Class

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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."