public Object setAttributeIfAbsent(String key, Object value) {
    """
	set attribute if key absent.
	
	@param key
	@param value
	@return
    """
        return attributes.putIfAbsent(key, value);
    }
public Object setAttributeIfAbsent(String key, Object value) {
        return attributes.putIfAbsent(key, value);
    }
public Object setAttributeIfAbsent ( String key , Object value ) { return attributes . putIfAbsent ( key , value ) ; }
set attribute if key absent.

@param key
@param value
@return
set attribute if key absent .