@Override
  public boolean containsCredential(String alias) throws AmbariException {
    Lock lock = getLock();
    lock.lock();
    try {
      return (alias != null) && !alias.isEmpty() && (cache.getIfPresent(alias) != null);
    } finally {
      lock.unlock();
    }
  }
Tests this CredentialStore for the existence of a credential with the specified alias
<p/>
This implementation is thread-safe, allowing one thread at a time to access the credential store.

@param alias a string declaring the alias (or name) of the credential
@return true if the alias exists; otherwise false
@throws AmbariException if an error occurs while searching forthe credential
ambari-server/src/main/java/org/apache/ambari/server/security/encryption/InMemoryCredentialStore.java