How to append text to an existing file in Java?

Optimize with BufferedWriter

Give your file manipulations a boost using BufferedWriter that provides an efficiency bonus for numerous write operations:

try (BufferedWriter bw = new BufferedWriter(new FileWriter("file.txt", true))) {
    bw.write("Appended text\n"); // Keep calm and carry on writing
    // Space for more writing operations
} catch (IOException e) {
    // Error handling, because prevention is better than cure
}
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BufferedWriter becomes handy when you have tons of writing operations - call it bulk-processing of your text append operations.

Leverage PrintWriter

For a more fluent syntax, adopt PrintWriter, lighting up your code with a richer set of methods similar to System.out.print:

try (PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("file.txt", true)))) {
    out.println("Appended text"); // Adding another pearl to the string
} catch (IOException e) {
    // Handle exceptions like a pro
}
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Unlock NIO.2 goodie bag

The NIO.2 package comes packed with Files and Paths classes, offering a modern and flexible alternative:

Path path = Paths.get("file.txt");
try {
    Files.write(path, Arrays.asList("Appended text"), StandardCharsets.UTF_8, StandardOpenOption.CREATE, StandardOpenOption.APPEND);
} catch (IOException e) {
    // If it ain't broken, catch exceptions
}
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The CREATE attribute with Files.write will do the charm of manifesting the file if it's not already there, saving you from a FileNotFoundException.

Don't let encoding and safety slip

When you're in the realm of file manipulation, never overlook encodings and safety:

• Explicitly state the character encoding (for example, StandardCharsets.UTF_8) to ensure text consistency across different environments.

Files.writeString(path, "Appended text", StandardOpenOption.APPEND, StandardCharsets.UTF_8);
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• Implement exception handling and handle resource management carefully, especially with older Java versions.

Writer writer = null;
try {
    writer = new FileWriter("file.txt", true);
    writer.write("Appended text"); // Drawing on your file canvas
} finally {
    if (writer != null) {
        writer.close(); // Shut the door when you leave!
    }
}
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Third-party libraries to the rescue

Libraries like Apache's FileUtils can simplify text appending:

try {
    FileUtils.writeStringToFile(new File("file.txt"), "Appended text", Charset.defaultCharset(), true);
} catch (IOException e) {
    // Exception handling, covering your back
}
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Let FileUtils know that you're appending, not overwriting, by using true as the last argument.

Navigating file paths

Before making your mark, ensure you're planted firmly in your directories:

Files.createDirectories(path.getParent()); // Ensuring you know where your files hangout
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This step guarantees that all parent directories are ready and set before you write the file, evading potential application crashes.