How do I create a file and write to it?

Note that each of the code samples below may throw IOException. Try/catch/finally blocks have been omitted for brevity. See this tutorial for information about exception handling.
Note that each of the code samples below will overwrite the file if it already exists
Creating a text file:
PrintWriter writer = new PrintWriter(“the-file-name.txt”, “UTF-8”);
writer.println(“The first line”);
writer.println(“The second line”);
writer.close();

Creating a binary file:
byte data[] = …
FileOutputStream out = new FileOutputStream(“the-file-name”);
out.write(data);
out.close();

Java 7+ users can use the Files class to write to files:
Creating a text file:
List lines = Arrays.asList(“The first line”, “The second line”);
Path file = Paths.get(“the-file-name.txt”);
Files.write(file, lines, StandardCharsets.UTF_8);
//Files.write(file, lines, StandardCharsets.UTF_8, StandardOpenOption.APPEND);

Creating a binary file:
byte data[] = …
Path file = Paths.get(“the-file-name”);
Files.write(file, data);
//Files.write(file, data, StandardOpenOption.APPEND);

In Java 7 and up:
try (Writer writer = new BufferedWriter(new OutputStreamWriter(
new FileOutputStream(“filename.txt”), “utf-8”))) {
writer.write(“something”);
}

There are useful utilities for that though:

FileUtils.writeStringtoFile(..) from commons-io
Files.write(..) from guava

Note also that you can use a FileWriter, but it uses the default encoding, which is often a bad idea – it’s best to specify the encoding explicitly.
Below is the original, prior-to-Java 7 answer

Writer writer = null;

try {
writer = new BufferedWriter(new OutputStreamWriter(
new FileOutputStream(“filename.txt”), “utf-8”));
writer.write(“Something”);
} catch (IOException ex) {
// Report
} finally {
try {writer.close();} catch (Exception ex) {/*ignore*/}
}

See also: Reading, Writing, and Creating Files (includes NIO2).