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Java.io.CharArrayReader Class in Java - GeeksforGeeks

Last Updated : 18 Apr, 2022

java.io.CharArrayReader class creates a character buffer using a character array.

Declaration: 

public class CharArrayReader
   extends Reader

Constructor :  

• CharArrayReader(char[] char_array) : Creates a CharArrayReader from a specified character array.
• CharArrayReader(char[] char_array, int offset, int maxlen) : Creates a CharArrayReader from a specified part of character array.

Methods:  

• read() : java.io.CharArrayReader.read() reads a single character and returns  -1 if end of the Stream is reached. 
  Syntax : 

public int read()
Parameters : 
-----------
Return  :
Returns read character as an integer ranging from range 0 to 65535.
-1 : when end of file is reached.

• read(char[] char_array, int offset, int maxlen) : java.io.CharArrayReader.read(char[] char_array, int offset, int maxlen)) reads a single character and returns -1 if end of the Stream is reached 
  Syntax : 

public int read(char[] char_array, int offset, int maxlen))
Parameters : 
char_array : destination array  
offset : starting position from where to store characters
maxlen : maximum no. of characters to be read
Return  :
Returns all the characters read
-1 : when end of file is reached.

• ready() : java.io.CharArrayReader.ready() checks whether the Stream is ready to be read or not. 
  CharArrayReader are always ready to be read. 
  Syntax : 

public boolean ready()
Parameters : 
-----------
Return  :
true if CharArrayReader is ready to be read.

• skip(long char) : java.io.CharArrayReader.skip(long char_no) skips 'char_no' no. of characters.  If n is negative, then this method does nothing and returns 0. 
  Syntax : 

public long skip(long char)
Parameters : 
char_no : char no. of characters to be skipped
Return  :
no. of characters skipped
Exception : 
IOException : In case of I/O error occurs

// Java program illustrating the working of CharArrayReader class methods
// read(), skip(), ready()
// read(char[] char_array, int offset, int maxlen)

import java.io.*;
public class NewClass
{
    public static void main(String[] args) throws IOException
    {

        // Initializing the character array
        char[] geek = {'G', 'E', 'E', 'K', 'S'};

        // Initializing the char_array
        CharArrayReader char_array1 = new CharArrayReader(geek);
        CharArrayReader char_array2 = new CharArrayReader(geek);

        // Use of ready() method
        boolean check1 = char_array1.ready();
        if(check1 ==true)
            System.out.println("char_array1 is ready");
        else
            System.out.println("char_array1 is not ready");


        int a = 0;
        System.out.print("Use of read() method : ");
        // Use of read() method : reading each character one by one
        while((a = char_array1.read()) != -1)
        {
            char c1 = (char)a;
            System.out.println(c1);

            // Use of skip() method
            long char_no = char_array1.skip(1);
            System.out.println("Characters Skipped : "+(c1+1));

        }
        System.out.println("");


        // Use of ready() method
        boolean check2 = char_array2.ready();
        if(check2 ==true)
            System.out.println("char_array2 is ready");
        else
            System.out.println("char_array2 is not ready");


  // Use of read(char[] char_array, int offset, int maxlen) : reading a part of array
        char_array2.read(geek, 1, 2);

        int b = 0;

  System.out.print("Use of read(char[] char_array, int offset, int maxlen) method : ");

        while((b = char_array2.read()) != -1)
        {
            char c2 = (char)b;
            System.out.print(c2);
        }

    }
}

Output : 

char_array1 is ready
Use of read() method : G
Characters Skipped : 72
E
Characters Skipped : 70
S
Characters Skipped : 84

char_array2 is ready
Use of read(char[] char_array, int offset, int maxlen) method : EKS

• mark(int readLimit) : java.io.CharArrayReader.mark(int readLimit) marks the current position in the Stream upto which the character can be read. This method always invokes reset() method. Subsequent calls to reset() will reposition the stream to this point. 
  Syntax : 

public long mark(int readLimit)
Parameters : 
readLimit : No. of characters that can be read up to the mark
Return  :
void
Exception : 
IOException : In case of I/O error occurs

• markSupported() : java.io.CharArrayReader.markSupported() tells whether the mark method is supported by the stream or not. 
  Syntax : 

public boolean markSupported()
Parameters : 
-------
Return  :
true if the mark method is supported by the stream
Exception : 
IOException : In case of I/O error occurs

• reset() : java.io.CharArrayReader.reset() Resets the stream to the most recent mark, or to the beginning if it has never been marked. 
  Syntax : 

public void reset()
Parameters : 
-------
Return  :
void
Exception : 
IOException : In case of I/O error occurs

• close() : java.io.CharArrayReader.close() closes the stream and reallocates the resources that were allotted to it. 
  Syntax : 

public void close()
Parameters : 
-------
Return  :
void
Exception : 
IOException : In case of I/O error occurs

// Java program illustrating the working of FilterInputStream method
// mark(), reset()
// markSupported(), close()

import java.io.*;
public class NewClass
{
    public static void main(String[] args) throws Exception
    {
        // Initializing CharArrayReader
        CharArrayReader char_array = null;
        char[] geek = {'H', 'E', 'L', 'L', 'O', 'G',  'E',  'E',  'K', 'S'};

        try
        {
            char_array = new CharArrayReader(geek);

            // read() method : reading and printing Characters
            // one by one
            System.out.println("Char : "+(char)char_array.read());
            System.out.println("Char : "+(char)char_array.read());
            System.out.println("Char : "+(char)char_array.read());

            // mark() : read limiting the 'geek' input stream
            char_array.mark(0);

            System.out.println("mark() method comes to play");
            System.out.println("Char : "+(char)char_array.read());
            System.out.println("Char : "+(char)char_array.read());
            System.out.println("Char : "+(char)char_array.read());

            // Use of markSupported() :
            boolean check = char_array.markSupported();
            if (check == true )
                System.out.println("mark() supported\n");

            if (char_array.markSupported())
            {
                // reset() method : repositioning the stream to
                // marked positions.
                char_array.reset();
                System.out.println("reset() invoked");
                System.out.println("Char : "+(char)char_array.read());
                System.out.println("Char : "+(char)char_array.read());
            }
            else
                System.out.println("mark() method not supported.");
            
        }
        catch(Exception excpt)
        {
            // in case of I/O error
            excpt.printStackTrace();
        }
        finally
        {
            // Use of close() : releasing the resources back to the
            // GarbageCollector when closes
            if(char_array != null)
                char_array.close();
        }
    }
}

Output : 

Char : H
Char : E
Char : L
mark() method comes to play
Char : L
Char : O
Char : G
mark() supported

reset() invoked
Char : L
Char : O

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