Java - CharArrayReader close() method

Description

The Java CharArrayReader close() method is used to close the stream and release any system resources associated with it. Once a CharArrayReader is closed, subsequent read or mark/reset operations on it will throw an IOException. However, since CharArrayReader operates on an in-memory character array and does not use external resources, closing it is more of a formality.

Declaration

Following is the declaration for java.io.CharArrayReader.close() method −

public void close()

Parameters

NA

Return Value

The method doesn't return any value.

Exception

NA

Example - Using CharArrayReader close() method

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) {      
	  CharArrayReader car = null;
      char[] ch = {'H', 'E', 'L', 'L', 'O'};

      try {
         // create new character array reader
         car = new CharArrayReader(ch);
         
         // closes the character array stream
         car.close();
         
         // read the character array stream
         car.read();
                  
      } catch(IOException e) {
         // if I/O error occurs
         System.out.print("Stream is already closed");
      } finally {
         // releases any system resources associated with the stream
         if(car!=null)
            car.close();
      }
   }
}

Output

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

Stream is already closed

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 - Handling a Closed Reader

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 = "Java Programming".toCharArray();

      // Create a CharArrayReader
      CharArrayReader reader = new CharArrayReader(data);

      try {
         // Read a few characters
         System.out.println("Reading some characters:");
         for (int i = 0; i < 5; i++) {
            System.out.print((char) reader.read());
         }
         System.out.println();

         // Close the reader
         reader.close();
         System.out.println("CharArrayReader closed.");

         // Attempt to read after closing the stream
         System.out.println("Trying to read after closing:");
         int charData = reader.read();
         if (charData == -1) {
            System.out.println("End of stream reached (or reader is closed).");
         }
      } catch (IOException e) {
         System.err.println("IOException: " + e.getMessage());
      }
   }
}

Output

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

Reading some characters:
Java 
CharArrayReader closed.
Trying to read after closing:
IOException: Stream closed

Explanation

• A CharArrayReader is initialized with "Java Programming".

• A few characters are read and printed.

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

• After closing, an attempt to read from the reader fails, as it is no longer usable. The read() method returns -1 to indicate the end of the stream or that the reader is closed.

Key Points

• Purpose−

  • The close() method is used to release resources, even if they are minimal in the case of CharArrayReader.

  • It is good practice to always close a reader when done, especially in larger applications.

• Behavior After Close−

  • After calling close(), any further read operations on the CharArrayReader will throw an IOException.

  • Mark/reset functionality will also become unavailable.

• Practicality−

  • While not strictly required for in-memory streams like CharArrayReader, calling close() ensures proper handling and makes the code consistent with other streams that do require explicit closure.