protected static Boolean getBooleanValue(Map<?, ?> map, String key) {
    return getBooleanValue(map, key, null);
  }
Safely retrieves the requested value (converted to a Boolean) from the supplied Map
<p/>
The found value will be converted to a Boolean using {@link Boolean#valueOf(String)}.
If not found, <code>null</code> will be returned

@param map a Map containing the relevant data
@param key a String declaring the item to retrieve
@return a Boolean representing the requested data; or null if not found
@see Boolean#valueOf(String)
@see #getBooleanValue(Map, String, Boolean)
ambari-server/src/main/java/org/apache/ambari/server/state/kerberos/AbstractKerberosDescriptor.java