Question

Are there any implementations of a static size hashtable that limits the entries to either the most recently or most frequently used metadata? I would prefer not to keep track of this information myself.

I know most caching components keep track of this, but I would rather not introduce quite a lot of new dependencies.

Answer 1

You can build an LRU cache using the standard JDK library using LinkedHashMap:

public class MyLRUCache<K, V> extends LinkedHashMap<K, V> {

    private final int maxEntries;

    public MyLRUCache(int maxEntries) {
        // you can be a bit fancy with capacity and load factor
        super(16, 0.75, true);
        this.maxEntries = maxEntries;
    }

    @Override
    protected boolean removeEldestEntry(Map.Entry<K, V> eldest) {
        return size() > maxEntries;
    }
}

You may want to play with WeakReferences as well.