OutputStreamWriter

OutputStreamWriter is a bridge from character streams to byte streams in Java I/O. It writes characters to an underlying OutputStream by encoding the characters into bytes using a specified charset. As a subclass of Writer, it participates in the character stream API and can be used wherever a Writer is expected.

Constructors allow different ways to specify the encoding: OutputStreamWriter(OutputStream out), OutputStreamWriter(OutputStream out, Charset cs), and OutputStreamWriter(OutputStream out, String charsetName). If no charset is provided, the platform’s default charset is used, which can affect portability across different environments.

Encoding behavior: OutputStreamWriter relies on a CharsetEncoder to convert characters to bytes. If a character cannot be encoded in the chosen charset, an encoding error may be reported during writing, typically resulting in an IOException being thrown.

Performance and usage notes: OutputStreamWriter performs no buffering by itself. For improved performance when writing many characters, wrap it in a BufferedWriter or use a higher-level writer. It is not guaranteed to be thread-safe; if multiple threads access the same writer, external synchronization is recommended or a thread-safe wrapper should be used.

Common usage: To write text to a file, create a FileOutputStream and wrap it with an OutputStreamWriter, optionally specifying a charset, such as new OutputStreamWriter(new FileOutputStream("out.txt"), StandardCharsets.UTF_8). Using try-with-resources ensures proper closure of the stream.

See also: InputStreamReader, FileWriter, PrintWriter.