Build a small LRU cache with LinkedHashMap

import java.util.LinkedHashMap;
import java.util.Map;

/** A fixed-capacity, thread-confined LRU cache built on LinkedHashMap. */
public final class LruCache<K, V> extends LinkedHashMap<K, V> {

    private static final long serialVersionUID = 1L;
    private final int capacity;

    public LruCache(int capacity) {
        super(Math.max(16, capacity * 2), 0.75f, true); // true = access order
        if (capacity <= 0) {
            throw new IllegalArgumentException("capacity must be positive");
        }
        this.capacity = capacity;
    }

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

    public static void main(String[] args) {
        var cache = new LruCache<String, Integer>(2);
        cache.put("a", 1);
        cache.put("b", 2);
        cache.get("a");     // "a" becomes the most recently used
        cache.put("c", 3);  // evicts "b"
        System.out.println(cache.keySet()); // [a, c]
    }
}