code: public boolean optBoolean( String key, boolean defaultValue ) {
        verifyIsNull();
        try{
           return getBoolean( key );
        }catch( Exception e ){
           return defaultValue;
        }
     }
docs: Get an optional boolean associated with a key. It returns the defaultValue
  if there is no such key, or if it is not a Boolean or the String "true" or
  "false" (case insensitive).
  
  @param key A key string.
  @param defaultValue The default.
  @return The truth.