@Override
    public Boolean getBooleanWithDefault(final String key, Boolean defaultValue) {

        return retrieve(new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                return configuration.getBoolean(key);
            }
        }, defaultValue);
    }
@ Override public Boolean getBooleanWithDefault ( final String key , Boolean defaultValue ) { return retrieve ( new Callable < Boolean > ( ) { @ Override public Boolean call ( ) throws Exception { return configuration . getBoolean ( key ) ; } } , defaultValue ) ; }
Get a Boolean property or a default value when property cannot be found
in any configuration file.

@param key          the key used in the configuration file.
@param defaultValue Default value returned, when value cannot be found in
configuration.
@return the value of the key or the default value.