FileWriter Class in Java

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

Table of Contents

1. Introduction
2. Creating a FileWriter
3. Writing Data to a File
4. Closing the Stream
5. Complete Example
6. Conclusion

Introduction

The FileWriter class is a subclass of OutputStreamWriter and is designed for writing character files. It is used to write data to files in the form of characters, making it ideal for text files. The FileWriter class writes data as a stream of characters and supports various methods for writing characters, arrays of characters, and strings.

Creating a FileWriter

To create a FileWriter, you need to provide the name of the file you want to write to. You can do this by passing a String representing the file path, a File object, or a FileDescriptor object to the FileWriter constructor. You can also specify whether to append to the file or overwrite it.

Example

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

public class FileWriterExample {
    public static void main(String[] args) {
        try {
            // Creating FileWriter using file path
            FileWriter fw1 = new FileWriter("example.txt");

            // Creating FileWriter using File object
            File file = new File("example.txt");
            FileWriter fw2 = new FileWriter(file);

            // Creating FileWriter using FileDescriptor
            FileDescriptor fd = FileDescriptor.out; // Placeholder for actual FileDescriptor
            FileWriter fw3 = new FileWriter(fd);

            // Creating FileWriter with append mode
            FileWriter fw4 = new FileWriter("example.txt", true);

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

Writing Data to a File

The FileWriter class provides several methods to write data to the file:

• void write(int c): Writes a single character.
• void write(char[] cbuf): Writes characters from an array.
• void write(char[] cbuf, int off, int len): Writes up to len characters from an array starting at offset off.
• void write(String str): Writes a string.
• void write(String str, int off, int len): Writes a portion of a string.

Example

import java.io.FileWriter;
import java.io.IOException;

public class FileWriterWriteExample {
    public static void main(String[] args) {
        try (FileWriter fw = new FileWriter("example.txt")) {
            String data = "Hello, World!";
            fw.write(data);
            System.out.println("Data written to file successfully.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Closing the Stream

It is important to close the FileWriter 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.FileWriter;
import java.io.IOException;

public class FileWriterCloseExample {
    public static void main(String[] args) {
        FileWriter fw = null;
        try {
            fw = new FileWriter("example.txt");
            String data = "Hello, World!";
            fw.write(data);
            System.out.println("Data written to file successfully.");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (fw != null) {
                    fw.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.FileWriter;
import java.io.IOException;

public class FileWriterTryWithResourcesExample {
    public static void main(String[] args) {
        try (FileWriter fw = new FileWriter("example.txt")) {
            String data = "Hello, World!";
            fw.write(data);
            System.out.println("Data written to file successfully.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Complete Example

Here is a complete example demonstrating the creation, writing, and closing of a FileWriter.

FileWriterExample.java

import java.io.FileWriter;
import java.io.IOException;

public class FileWriterExample {
    public static void main(String[] args) {
        try (FileWriter fw = new FileWriter("example.txt")) {
            String data = "Hello, World!";
            fw.write(data);
            System.out.println("Data written to file successfully.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Conclusion

The FileWriter class in Java is used for writing character data to files. By understanding how to create, write, and close a FileWriter, 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.