Question

I want an implementation of Map that has a maximum size. I want to use this as a cache and so oldest entries are removed once limit has been reached.

I also don’t want to introduce a dependency on any 3rd party libraries.

Answer 1

You can use LinkedHashMap like this

You can remove by LRU or FIFO.

public static <K, V> Map<K, V> createLRUMap(final int maxEntries) {
    return new LinkedHashMap<K, V>(maxEntries*10/7, 0.7f, true) {
        @Override
        protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
            return size() > maxEntries;
        }
    };
}