@Override
      public ReentrantLock createObject(K key) {
        return new ReentrantLock();
      }
A utility class to manage a set of locks. Each lock is identified by a String which serves as a
key. Typical usage is:

<pre>
class Example {
  private final static KeyLocker&lt;String&gt; locker = new Locker&lt;String&gt;();

  public void foo(String s) {
    Lock lock = locker.acquireLock(s);
    try {
      // whatever
    } finally {
      lock.unlock();
    }
  }
}
</pre>
hbase-common/src/main/java/org/apache/hadoop/hbase/util/KeyLocker.java