Java FileReader

Input/Output: Exploring java.io > Character Streams >
Siva Nookala - 14 Apr 2016

Convenience class for reading character files. The constructors of this class assume that the default character encoding and the default byte-buffer size are appropriate. To specify these values yourself, construct an InputStreamReader on a FileInputStream.

FileReader is meant for reading streams of characters. For reading streams of raw bytes, consider using a Java FileInputStream.

FileReader Constructors:

Constructor	Description
`FileReader(File file)`	Creates a new `FileReader`, given the `File` to read from.
`FileReader(FileDescriptor fd)`	Creates a new `FileReader,` given the `FileDescriptor` to read from.
`FileReader(String fileName)`	Creates a new `FileReader`, given the name of the file to read from.

Once you have FileReader object in hand then there is a list of helper methods which can be used manipulate the files.

FileReader Methods:

Method	Description
`int read() throws IOException`	Reads a single character. Returns an `int`, which represents the character read.
`int read(char [] c, int offset, int len)`	Reads characters into an array. Returns the number of characters read.

Example Program:

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class FileReaderWriter{

    public static void main(String args[]) throws IOException{

        File file = new File("Output.txt"); //LINE A

        // creates the file
        file.createNewFile();

        // creates a FileWriter Object
        FileWriter fw = new FileWriter(file); 

        // writes the content to the file
        fw.write("This\nis\nJava\nMerit\nCampus."); // LINE B
        fw.flush();
        fw.close();

        // creates a FileReader Object
        FileReader fr = new FileReader(file); 
        char [] output = new char[50];

        fr.read(output); // reads the content to the array

        for(char out : output)
        {
            System.out.print(out); // prints the characters one by one
        }

        fr.close();
    }
}

Output:

This
is
Java
Merit
Campus.

Description:
A text file Output.txt is taken and created. Input is taken into the FileWriter and is written onto the file. The file is read using FileReader and printed.

Things to try:

Try giving other inputs to File in LINE A.

Try giving other inputs to FileWriter in LINE B like "Your Online Java School"<cw>, "Don't just learn Java, do Java".

Java Writer Class

Java FileWriter