This project represents few small benchmark classes to see how primitive types compares to theirs wrappers.

I measured three times the creation of one million of int, long, empty custom class vs Object and custom class containing long primitive

From the quick benchmark I found out:

1. measuring integers

• wrapper class needs 4.5 (20/4) times more memory than int
• the time overhead is about 12 times

1. measuring long

• wrapper class took 3.5 (28/8) more memory than long
• the time overhead was comparable to int overhead, about 12 times
• Long wrapper is comparable to creating custom class with long primitive field (quite obvious from the definition)

1. measuring empty class vs empty object

• not significant difference

1. measuring methods

• using Runtime class to get used memory is not precise enough
• to get precise output I used object explorer library (http://code.google.com/p/memory-measurer/)
• I used MacBookAir 1.7Ghz CPU, JDK1.6.0_31 64bit by [Michal Antolik]

##console output##

--- more precise using object explorer library
Measuring integers
	primitive Type: Average: 3906.27 KB of memory, took 0.00 seconds (memory size per unit: 4)
	wrapper Type: Average: 19531.27 KB of memory, took 0.05 seconds (memory size per unit: 20)
	memory wrapper overhead: 4
	consumed time wrapper overhead: 12
Measuring long numbers
	primitive Type: Average: 7812.52 KB of memory, took 0.01 seconds (memory size per unit: 8)
	wrapper Type: Average: 27343.77 KB of memory, took 0.06 seconds (memory size per unit: 28)
	memory wrapper overhead: 3
	consumed time wrapper overhead: 12
Measuring empty class instantiating
	Empty class: Average: 19531.27 KB of memory, took 0.04 seconds (memory size per unit: 20)
	Empty object: Average: 19531.27 KB of memory, took 0.05 seconds (memory size per unit: 20)
	Measuring emulated long class instantiating
	Emulated long class: Average: 27343.77 KB of memory, took 0.07 seconds (memory size per unit: 28)

 
--- less precise
Measuring integers
	primitive Type: Average: 4331.07 KB of memory, took 0.03 seconds (memory size per unit: 4)
	wrapper Type: Average: 25162.66 KB of memory, took 0.15 seconds (memory size per unit: 25)
	memory wrapper overhead: 5
	consumed time wrapper overhead: 4
Measuring long numbers
	primitive Type: Average: 8107.86 KB of memory, took 0.03 seconds (memory size per unit: 8)
	wrapper Type: Average: 27542.90 KB of memory, took 0.07 seconds (memory size per unit: 28)
	memory wrapper overhead: 3
	consumed time wrapper overhead: 2
Measuring empty class instantiating
	Empty class: Average: 25156.73 KB of memory, took 0.17 seconds (memory size per unit: 25)
	Empty object: Average: 25176.66 KB of memory, took 0.18 seconds (memory size per unit: 25)
	Measuring emulated long class instantiating
	Emulated long class: Average: 27376.90 KB of memory, took 0.12 seconds (memory size per unit: 28)