FileWriter is a character stream class used to write character data (text) to a file. It is part of the java.io package and is used for writing text files.
Commonly Used Constructors and Methods
Simple Program
Mahesh wants to write a greeting message to a file named greeting.txt using FileWriter.
import java.io.FileWriter;
import java.io.IOException;
public class FileWriterExample {
public static void main(String[] args) {
try (FileWriter fw = new FileWriter("greeting.txt")) {
fw.write("Hello, LotusJavaPrince!");
System.out.println("Message written successfully.");
} catch (IOException e) {
System.out.println("Error: " + e.getMessage());
}
}
}Content of greeting.txt after execution:
Hello, LotusJavaPrince!Output:
Message written successfully.Problem Statement:
LotusJavaPrince wants to create a log system that writes a list of tasks performed into a file log.txt. The system should:
- Append tasks instead of overwriting.
- Record the timestamp and task description.
import java.io.FileWriter;
import java.io.IOException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
public class TaskLogger {
public static void main(String[] args) {
String[] tasks = {
"Started banking module.",
"User authenticated.",
"Transaction processed.",
"Session terminated."
};
try (FileWriter fw = new FileWriter("log.txt", true)) { // append mode
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
for (String task : tasks) {
String log = dtf.format(LocalDateTime.now()) + " - " + task + "\n";
fw.write(log);
}
System.out.println("Log written successfully.");
} catch (IOException e) {
System.out.println("Error writing log: " + e.getMessage());
}
}
} Sample Content of log.txt after multiple executions:
2025-05-30 10:42:18 - Started banking module.
2025-05-30 10:42:18 - User authenticated.
2025-05-30 10:42:18 - Transaction processed.
2025-05-30 10:42:18 - Session terminated.Code language: CSS (css)FileWriter is perfect for writing text data to files in a character-oriented way.
- It is often used with
BufferedWriterfor performance optimization. - Use the append constructor (
FileWriter(String, boolean)) to preserve existing file content. - It’s not suitable for binary files (images, PDFs)—use
FileOutputStreamfor that.