Java Writer Class

The Java Writer class is an abstract class in the java.io package used for writing character-based data to an output destination. It serves as the base class for character output classes such as FileWriter, BufferedWriter, and StringWriter.

• Supports writing characters, character arrays, and strings.
• Provides common operations such as write(), append(), flush(), and close().

Declaration of the Writer Class

public abstract class Writer implements Appendable, Closeable, Flushable

Since it’s an abstract class, we can’t instantiate it directly; instead, we use concrete subclasses like FileWriter, BufferedWriter or PrintWriter.

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

public class Geeks {
    public static void main(String[] args)
    {
        try {
          
            // Create a FileWriter to write to a file named "example.txt"
            FileWriter w = new FileWriter("example.txt");

            // Write a simple message to the file
            w.write("Hello, World!");

            // Close the writer
            w.close();

            System.out.println("Message written");
        }
        catch (IOException e) {
            System.out.println("An error occurred: " + e.getMessage());
        }
    }
}

Message written

Explanation: Creates a FileWriter object to write "Hello, World!" into example.txt. After writing, it closes the stream to ensure data is saved and resources are released.

Constructors of the Writer Class

The Writer class in Java has two protected constructors that allow for the creation of character streams with synchronization capabilities.

• Protected Writer(): Creates a new character stream that can itself synchronize on the writer.
• protected Writer(Object obj): Creates a new character stream that can itself synchronize on the given object – ‘obj’.

Example: Writing Characters to a File

import java.io.*;

public class GFG{
    public static void main(String[] args)
    {
        try {
            Writer writer = new FileWriter("example.txt");
            writer.write("Hello, Java Writer Class!");
            writer.close();
            System.out.println(
                "Data written successfully.");
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Data written successfully.

Output File: example.txt

Explanation: Creates a FileWriter instance to write text data to example.txt. Writes the message "Hello, Java Writer Class!" and closes the writer to finish safely.

Example: Using BufferedWriter for Efficiency

import java.io.*;

public class GFG{
    public static void main(String[] args)
    {
        try (Writer writer = new BufferedWriter(
                 new FileWriter("buffered.txt"))) {
            writer.write(
                "BufferedWriter makes writing more efficient.");
            writer.write(
                "\nIt reduces disk I/O by using a buffer.");
            System.out.println(
                "Data written using BufferedWriter.");
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Data written using BufferedWriter.

Output File: buffered.txt

Explanation: Uses BufferedWriter to improve performance by temporarily storing data before writing it. Writes two lines of text into buffered.txt and automatically closes the stream using try-with-resources.

Example: Appending Data to a File

import java.io.*;

public class GFG{
    public static void main(String[] args) {
        try (Writer writer = new FileWriter("example.txt", true)) {
            writer.write("\nThis line was appended later.");
            System.out.println("Data appended successfully.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Data appended successfully.

Output File: example.txt

Explanation: Opens the existing file example.txt in append mode by passing true to FileWriter. Adds a new line "This line was appended later." without overwriting the previous data.

Java Writer Class Methods

There are certain methods associated with the Java Writer class as mentioned below: