The MutableAttributeSet interface adds six methods to add and remove attributes from the set:
public void addAttribute(Object name, Object value)
public void addAttributes(AttributeSet attributes)
public void removeAttribute(Object name)
public void removeAttributes(Enumeration names)
public void removeAttributes(AttributeSet attributes)
public void setResolveParent(AttributeSet parent)
Again the values are strings and the names are HTML.Attribute objects.