package my.super.duper.test.package;

import org.apache.commons.lang.ArrayUtils;

import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.List;

/**
 * Benchmarks conversion from List<Integer> to int[] for different
 * size lists using pure java vs Apache Commons ArrayUtils.
 */
public class ArrayUtilsBenchmark
{
    private final static DecimalFormat DF = new DecimalFormat("#.##");

    public static void main(String[] args)
    {
        // run loops 1M times to warm up
        ArrayUtilsBenchmark test = new ArrayUtilsBenchmark();
        test.test(1000000);

        for (int i=2;i<2561;i+=i) {
            ArrayUtilsBenchmark testClass = new ArrayUtilsBenchmark();
            testClass.test(i);
        }
    }

    private void test(int numElements) {

        List<Integer> list1 = new ArrayList<Integer>(numElements);
        for (int i=0; i<numElements; i++) {
            list1.add(new Integer(i*((int)(Math.random()*100))));
        }

        System.out.println("Comparison for " + list1.size() + " elements");

        long start1 = System.nanoTime();
        int[] primList1 = convertPureJava(list1);
        final double dur1 = System.nanoTime() - start1;
        System.out.println("pure java:   " + (long)dur1 + " ns");

        long start2 = System.nanoTime();
        int[] primList2 = convertArrayUtils(list1);
        final double dur2 = System.nanoTime() - start2;
        System.out.println("array utils: " + (long)dur2 + " ns");

        System.out.println("factor: "+ DF.format(dur1/dur2));
        System.out.println("----------------------------");
    }

    private static int[] convertPureJava(List<Integer> list)
    {
        int[] arrayOfInt = new int[list.size()];
        int i = 0;

        for (Integer tutId : list) {
            arrayOfInt[i] = tutId;
            i++;
        }

        return arrayOfInt;
    }

    private static int[] convertArrayUtils(List<Integer> list)
    {
        return ArrayUtils.toPrimitive(list.toArray(new Integer[list.size()]));
    }
}