A simple striped lock

StripedLock.java

import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.locks.Lock;

/**
 * Striped lock impl for when proper concurrency libs (like guava) can't be used, either due to
 * dependency issues or other reasons.
 *
 * Returns (creates if not exists) a unique Lock for a given K
 *
 * @author Amit Narayanan
 */
public class StripedLock<K, L extends Lock>
{
    private ConcurrentMap<K, L> locks = new ConcurrentHashMap<K, L>();

    /**
     * For when creation of lock entails a simple new operator
     */
    public L getOrCreateLock(K key, Class<? extends L> lockClass) throws Exception
    {
        final L lock = lockClass.newInstance();
        return getLock(key, lock);
    }

    /**
     * For when creation of lock is more involved (say requires Conditions, or other custom stuff).
     */
    public L getOrCreateLock(K key, Callable<? extends L> lockCtor) throws Exception
    {
        final L lock = lockCtor.call();
        return getLock(key, lock);
    }

    private L getLock(final K key, final L newLock)
    {
        L lock = locks.putIfAbsent(key, newLock);
        return lock != null ? lock : newLock;
    }
}