A concurrency-safe rate limiter that executes a Runnable at most once per key, using ConcurrentHashMap and a sentinel marker. Cleanly implements a one-shot rate limiting pattern that can be reused in any Java application requiring per-key throttle or debounce behavior. The class is self-contained with no internal dependencies beyond standard Java libraries.

An immutable interval class supporting inclusive ranges with merge and subtract operations. Provides efficient handling of integer ranges (e.g., for ACK frame generation) and can be reused in any project requiring interval arithmetic. The implementation is clean, well-tested, and has no external dependencies.

Implements QUIC's variable-length integer encoding (1-8 bytes with 2-bit length prefix) for both ByteBuffer and InputStream. While specific to QUIC, the encoding pattern is reusable for any protocol needing compact integer representation. The class is self-contained, handles edge cases, and includes thorough parsing/serialization methods.

A controllable clock implementation for deterministic time management in unit tests. Supports setting the current time, advancing time, and registering listeners for time changes. This pattern is universally reusable for testing time-sensitive logic without relying on system clock or thread sleeps. Self-contained with no internal dependencies.

A reflection-based utility to set private fields on objects, bypassing access checks. Includes support for static fields and allows access to final fields by resetting the modifier. While specific to testing, this utility is widely applicable for injecting test dependencies or manipulating state in legacy code. Self-contained and handles Java module system limitations.