if (old instanceof MutableAttributeSet)
AttributeSet ret; if (old.getAttributeCount() + attributes.getAttributeCount() < getCompressionThreshold())
  public AttributeSet addAttributes(AttributeSet old, AttributeSet attributes)  {    if (old instanceof MutableAttributeSet)      {        ((MutableAttributeSet)old).addAttributes(attributes);        return old;      }    else       {        MutableAttributeSet mutable = createLargeAttributeSet(old);        mutable.addAttributes(attributes);        if (mutable.getAttributeCount() >= getCompressionThreshold())          return mutable;        else          {            SmallAttributeSet small = createSmallAttributeSet(mutable);            if (sharedAttributeSets.containsKey(small))              small = (SmallAttributeSet) sharedAttributeSets.get(small);            else              sharedAttributeSets.put(small,small);            return small;          }      }  }