Java FilterReader

Java FilterReader is used to perform filtering operation on reader stream. It is an abstract class for reading filtered character streams.

The FilterReader provides default methods that passes all requests to the contained stream. Subclasses of FilterReader should override some of its methods and may also provide additional methods and fields.

Field

Modifier	Type	Field	Description
protected	Reader	in	The underlying character-input stream.

Constructors

Modifier	Constructor	Description
protected	FilterReader(Reader in)	It creates a new filtered reader.

Method

Modifier and Type	Method	Description
void	close()	It closes the stream and releases any system resources associated with it.
void	mark(int readAheadLimit)	It marks the present position in the stream.
boolean	markSupported()	It tells whether this stream supports the mark() operation.
boolean	ready()	It tells whether this stream is ready to be read.
int	read()	It reads a single character.
int	read(char[] cbuf, int off, int len)	It reads characters into a portion of an array.
void	reset()	It resets the stream.
long	skip(long n)	It skips characters.

Example

In this example, we are using "javaFile123.txt" file which contains "India is my country" text in it. Here, we are converting whitespace with question mark '?'.

import java.io.*;
class CustomFilterReader extends FilterReader {
	CustomFilterReader(Reader in) {
		super(in);
	}
	public int read() throws IOException {
		int x = super.read();
		if ((char) x == ' ')
			return ((int) '?');
		else
			return x;
	}
}
public class FilterReaderExample {
	public static void main(String[] args) {
		try  {
			Reader reader = new FileReader("javaFile123.txt");
			CustomFilterReader fr = new CustomFilterReader(reader);
			int i;
			while ((i = fr.read()) != -1) {
				System.out.print((char) i);
			}
            fr.close();
            reader.close();
		} catch (Exception e) {
			e.getMessage();
		}
	}
}

Output: