A word processor uses the following code for defining font format:

class FontFormat inherits Object
  private fontName : String
  private fontSize : Int

  public constructor(name : String, size : Int)
    fontName = name
    fontSize = size
  end constructor

  public function getFontName() : String
    return fontName
  end function

  public function getFontSize() : Int
    return fontSize
  end function

  override public function equals(obj : Object) : Bool
    if (!(obj instanceof FontFormat))
      return false
    end if
    
    FontFormat f = (FontFormat)obj
    return f.getFontName() == fontName && f.getFontSize() == fontSize
  end function

  override public function getHashCode() : Int
    return fontName.getHashCode() ^ fontSize.getHashCode()
  end function
end class

Analysis shows that even the largest documents use fewer than a hundred different combinations of font name and size. The same analysis shows that the application sometimes uses thousands of FontFormat objects, most of which share the same font name and size.

(Fill in the blank with the software design pattern that solves the issue.)

The ____________ software design pattern can be used to minimize the memory footprint by sharing FontFormat objects.