The following text was written to the standard output stream when the ShapesThing.java program was executed from IntelliJ.
square = <Square: side=400.0> area of square = 160000.0 perimeter = 1600.0 diagonal = 565.685424949238 disk = <Circle: radius=200.0> area of disk = 125663.70614359173 perimeter of disk = 1256.6370614359173 diamond = <Square: side=282.842712474619> area of diamond = + 80000.0