Overview Java 8 didn’t just add Streams — it also enhanced the existing Iterable, Collection, List, and Map interfaces with default methods that cover the most common imperative patterns. Understanding these methods lets you write cleaner code even without streams. The three methods worth memorising immediately are computeIfAbsent (the most useful new Map method), merge (for accumulation patterns), and removeIf (eliminating the iterator-based removal pattern). Together they eliminate the most common sources of verbose boilerplate in collection-heavy code.