Java Autoboxing Performance: Unboxing Performance Example

how-to-convert-an-arraylist-to-an-int-array-in-java-with-unboxing.groovy

@Grab(group='com.jamonapi', module='jamon', version='2.82')
import com.jamonapi.Monitor
import com.jamonapi.MonitorFactory

import static java.util.Arrays.asList

import java.util.stream.Collectors
import java.util.List
import java.util.Arrays
import java.util.Random

def random = new Random()

def arrayCapacity = 10000

def numbers = new java.lang.Integer[arrayCapacity + 1]

for (int ctr in 0..arrayCapacity) {
    numbers[ctr] = java.lang.Integer.valueOf (random.nextInt())
}

def iterations = 100000

def result = null

def tempResult = asList (numbers)

result = new java.util.ArrayList (arrayCapacity) as java.util.List

result.addAll (tempResult)

def integerArray = new int[arrayCapacity + 1]

def monitor = MonitorFactory.start("Convert an ArrayList of Integer to an int array (int[]) performance monitor unboxing example.")

for (int outerCtr in 0..iterations) {
  for (int ctr in 0..arrayCapacity) {
    integerArray[ctr] = result.get(ctr)
  }
}

monitor.stop ()

println "Unboxing performance: $monitor"

return;

Unboxing takes place on line #38.

See also the section on Java Unboxing Performance in the article entitled Is autoboxing wrecking your Java application's performance?.