How to Use Java FileWriter to Append a Line to a Text File

How can I use Java's FileWriter to append a line to a text file?

FileWriter writer = new FileWriter("file.txt", true); // 'true' for append mode

Appending text to a file in Java can be easily achieved using the FileWriter class. By leveraging the append mode functionality, you can add new lines of text without overwriting existing data.

try {
    FileWriter writer = new FileWriter("file.txt", true);
    BufferedWriter bufferedWriter = new BufferedWriter(writer);
    bufferedWriter.write("This is a new line of text.");
    bufferedWriter.newLine(); // adds a new line
    bufferedWriter.close(); // don't forget to close the writer
} catch (IOException e) {
    e.printStackTrace();
}

Causes

• File may not exist prior to appending, causing create errors if not handled properly.
• File permissions may restrict write access during append operations.
• Incorrect path specified can lead to FileNotFound exceptions.

Solutions

• Use the second argument of FileWriter to be 'true' to enable append mode: new FileWriter("file.txt", true).
• Always check if the file exists before attempting to append to it, or create it if it does not.
• Handle potential IOExceptions with try-catch blocks to ensure the program doesn't crash on file operations.

Mistake: Neglecting to close the FileWriter or BufferedWriter, which can lead to resource leaks.

Solution: Always call close() method on the BufferedWriter after writing is complete.

Mistake: Not using append mode, resulting in overwriting existing file contents.

Solution: Set the append flag to true when creating the FileWriter.