Java.io.FilterReader class in Java

Abstract class for reading filtered character streams. The abstract class FilterReader itself provides default methods that pass all requests to the contained stream. Subclasses of FilterReader should override some of these methods and may also provide additional methods and fields.
Constructor :

  • protected FilterReader(Reader in) : Creates a new filtered reader.

Methods:

  • void close() : Closes the stream and releases any system resources associated with it.Once the stream has been closed, further read(), ready(), mark(), reset(), or skip() invocations will throw an IOException. Closing a previously closed stream has no effect.
    Syntax :public void close()
               throws IOException
    Throws:
    IOException
  • void mark(int readAheadLimit) : Marks the present position in the stream.
    Syntax :public void mark(int readAheadLimit)
              throws IOException
    Parameters:
    readAheadLimit - Limit on the number of characters that may be read 
    while still preserving the mark. After reading this many characters,
     attempting to reset the stream may fail.
    Throws:
    IOException
  • boolean markSupported() : Tells whether this stream supports the mark() operation.
    Syntax :public boolean markSupported()
    Returns:
    true if and only if this stream supports the mark operation.
  • int read() : Reads a single character.
    Syntax :public int read()
             throws IOException
    Returns:
    The character read, as an integer in the range 0 to 65535 (0x00-0xffff), 
    or -1 if the end of the stream has been reached
    Throws:
    IOException
  • int read(char[] cbuf, int off, int len) : Reads characters into a portion of an array.
    Syntax :public int read(char[] cbuf,
           int off,
           int len)
             throws IOException
    Parameters:
    cbuf - Destination buffer
    off - Offset at which to start storing characters
    len - Maximum number of characters to read
    Returns:
    The number of characters read, or -1 if the end of the stream has been reached
    Throws:
    IOException
  • boolean ready() : Tells whether this stream is ready to be read.
    Syntax :public boolean ready()
                  throws IOException
    Returns:
    True if the next read() is guaranteed not to block for input, 
    false otherwise. Note that returning false does not guarantee
    that the next read will block.
    Throws:
    IOException
  • void reset() : Resets the stream.
    Syntax :public void reset()
               throws IOException
    Throws:
    IOException
  • long skip(long n) : Skips characters.
    Syntax :public long skip(long n)
              throws IOException
    Parameters:
    n - The number of characters to skip
    Returns:
    The number of characters actually skipped
    Throws:
    IOException

Program :

filter_none

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code

//Java program illustrating FilterReader class methods
  
import java.io.*;
class FilterReaderdemo
{
    public static void main(String[] args) throws IOException
    {
        Reader r = new StringReader("GeeksforGeeks");
        FilterReader fr = new FilterReader(r) 
        {
        };
        char ch[] = new char[8];
          
        //illustrating markSupported()
        if(fr.markSupported())
        {
            //illustrating mark() method
            System.out.println("mark method is supported");
            fr.mark(100);
        }
          
        //illustrating skip() method
        fr.skip(5);
          
        //illustrating ready()
        if(fr.ready())
        {
            //illustrating read(char[] cbuff,int off,int len)
            fr.read(ch);
            for (int i = 0; i < 8; i++) 
            {
                System.out.print(ch[i]);
            }
              
            //illustrating reset()
            fr.reset();
            for (int i = 0; i <5 ; i++)
            {
                //illustrating read()
                System.out.print((char)fr.read());
            }
        }
          
        //closing the stream
        fr.close();
    }
}

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Output :

mark method is supported
forGeeksGeeks

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