Decorator Pattern in Java’s Popular Libraries

Real-World Decorator Pattern Implementations

In this article we will explore real-world Java libraries and frameworks that make use of the Decorator pattern internally.

First, it’s essential to grasp its significance and learn how to apply it.

Java: Why Decorator Design Pattern is Important

Java I/O (BufferedInputStream)

InputStream input = new BufferedInputStream(new FileInputStream("file.txt"));

BufferedInputStream wraps (decorates) a FileInputStream to add buffering capabilities, which improves reading performance by reducing the number of I/O operations performed on the file system.

Java I/O (DataInputStream)

DataInputStream dataInput = new DataInputStream(new BufferedInputStream(new FileInputStream("file.txt")));

DataInputStream decorates a BufferedInputStream to provide higher-level methods for reading Java primitives (like int, float, UTF, etc.) while still utilizing the buffering functionality for performance.