An LRU cache in Java
Java interview exercise on Collections, difficulty 3 of 3. Solve it in the editor beside a worked example, or cold in Interview mode with the example hidden; the tests run the moment you do.
Write LruCache<K, V> with a capacity given to the constructor, get(key) returning the value or null, put(key, value), and size(). Both get and put make the key the most recently used; when a put would exceed the capacity, the least recently used entry is evicted. A LinkedHashMap in access order (the three-argument constructor) does most of the work.
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Interview mode hides the example: solve it from memory, without the hint or the solution, and it counts as solved cold. Progress is saved in your browser, and in your account if you sign in.