FileReader Class in Java

The FileReader class in Java is part of the java.io package and is used to read character files. It provides a convenient way to read character data from a file, making it an essential class for file I/O operations involving text files.

Table of Contents

1. Introduction
2. Creating a FileReader
3. Reading Data from a File
4. Closing the Stream
5. Complete Example
6. Conclusion

Introduction

The FileReader class is a subclass of InputStreamReader and is designed for reading character files. It is used to read data from files in the form of characters, making it ideal for text files. The FileReader class reads data as a stream of characters and supports various methods for reading characters, arrays of characters, and lines of text.

Creating a FileReader

To create a FileReader, you need to provide the name of the file you want to read. You can do this by passing a String representing the file path, a File object, or a FileDescriptor object to the FileReader constructor.

Example

import java.io.FileReader;
import java.io.File;
import java.io.FileDescriptor;
import java.io.FileNotFoundException;

public class FileReaderExample {
    public static void main(String[] args) {
        try {
            // Creating FileReader using file path
            FileReader fr1 = new FileReader("example.txt");

            // Creating FileReader using File object
            File file = new File("example.txt");
            FileReader fr2 = new FileReader(file);

            // Creating FileReader using FileDescriptor
            FileDescriptor fd = FileDescriptor.in; // Placeholder for actual FileDescriptor
            FileReader fr3 = new FileReader(fd);

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

Reading Data from a File

The FileReader class provides several methods to read data from the file:

• int read(): Reads a single character.
• int read(char[] cbuf): Reads characters into an array.
• int read(char[] cbuf, int off, int len): Reads up to len characters into an array starting at offset off.

Example

import java.io.FileReader;
import java.io.IOException;

public class FileReaderReadExample {
    public static void main(String[] args) {
        try (FileReader fr = new FileReader("example.txt")) {
            int content;
            while ((content = fr.read()) != -1) {
                System.out.print((char) content);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Closing the Stream

It is important to close the FileReader after completing the file operations to release the system resources associated with the stream. This can be done using the close() method.

Example

import java.io.FileReader;
import java.io.IOException;

public class FileReaderCloseExample {
    public static void main(String[] args) {
        FileReader fr = null;
        try {
            fr = new FileReader("example.txt");
            int content;
            while ((content = fr.read()) != -1) {
                System.out.print((char) content);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (fr != null) {
                    fr.close();
                }
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }
}

Alternatively, you can use the try-with-resources statement, which ensures that the stream is closed automatically.

Example

import java.io.FileReader;
import java.io.IOException;

public class FileReaderTryWithResourcesExample {
    public static void main(String[] args) {
        try (FileReader fr = new FileReader("example.txt")) {
            int content;
            while ((content = fr.read()) != -1) {
                System.out.print((char) content);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Complete Example

Here is a complete example demonstrating the creation, reading, and closing of a FileReader.

FileReaderExample.java

import java.io.FileReader;
import java.io.IOException;

public class FileReaderExample {
    public static void main(String[] args) {
        try (FileReader fr = new FileReader("example.txt")) {
            int content;
            while ((content = fr.read()) != -1) {
                System.out.print((char) content);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Conclusion

The FileReader class in Java is used for reading character data from files. By understanding how to create, read, and close a FileReader, you can effectively handle file I/O operations involving text files in your Java applications. Remember to always close the stream after use to ensure that system resources are properly released.