Decorator pattern — InputStream wrappers example?

Decorator pattern

Decorator wraps an object to add behavior while preserving the same interface. Java I/O is the textbook case: InputStream decorators add buffering, decompression, or charset decoding without subclassing every combination.

• new BufferedInputStream(new FileInputStream(path)) — fewer syscalls.
• GZIPInputStream — transforms bytes on read; still an InputStream.
• Decorators are transparent to callers that only need the base type.
• Order matters: buffer around gzip vs gzip around buffer changes performance.

try (InputStream in = new BufferedInputStream(
        new GZIPInputStream(new FileInputStream("data.gz")))) {
    byte[] buf = in.readNBytes(4096);
}