What is the difference between Comparable and Comparator?

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Both define ordering, but in different places. Comparable — the class itself implements compareTo() , defining its natural ordering (e.g., String , Integer ). Single ordering per class. Comparator — an external ordering supplied via compare() . Lets you define many orderings without modifying the class. Often written as a lambda or built with Comparator.comparing(...) . Use — Comparable when there's one obvious order; Comparator when you need flexibility or work with classes you don't own. Know the difference: Comparable = natural ordering (one per class), Comparator = custom ordering (many possible). Show Java 8 Comparator factory methods (comparing, thenComparing, reversed). These are more concise than anonymous classes.