Use Enhanced For Loop Syntax is outputting slower result

Question

I was reading the Google documents page when I came across this article http://developer.android.com/training/articles/perf-tips.html

Can anyone explain why I'm getting the opposite results?

My results are: (on average) Result 1: 76 Result 2: 73 Result 3: 143

I performed some tests (looped over and over same tests) using the following code:

package TestPack;

import java.util.ArrayList;


public class Test
{
static ArrayList<Integer> mTheArray = new ArrayList<Integer>();
static
{
    for(int i = 0; i < 10000000; i++)
    {
        mTheArray.add(1234234223);
    }
}

static long mTimeStarted;
public static void main(String args[])
{
    //Test 1.
    mTimeStarted = System.currentTimeMillis();
    One();
    Fn.Out("Result 1: " + String.valueOf(System.currentTimeMillis() - mTimeStarted));

    //Test 2.
    mTimeStarted = System.currentTimeMillis();
    Two();
    Fn.Out("Result 2: " + String.valueOf(System.currentTimeMillis() - mTimeStarted));

    //Test 3
    mTimeStarted = System.currentTimeMillis();
    Three();
    Fn.Out("Result 3: " + String.valueOf(System.currentTimeMillis() - mTimeStarted));

}

//Slowest (But not...).
public static int One()
{
    int sum = 0;
    for (int i = 0; i < mTheArray.size(); ++i) 
    {
        sum += mTheArray.get(i);
    }
    return sum;
}

public static int Two()
{
    int sum = 0;
    ArrayList<Integer> localArray = mTheArray;
    int len = localArray.size();

    for (int i = 0; i < len; ++i) {
        sum += localArray.get(i);
    }
    return sum;
}

//Fastest (But actually slowest in this test).
public static int Three()
{
    int sum = 0;
    for (Integer a : mTheArray) {
        sum += a;
    }
    return sum;
}

}

Answer 1

The page you linked specifically states that:

With an ArrayList, a hand-written counted loop is about 3x faster (with or without JIT), but for other collections the enhanced for loop syntax will be exactly equivalent to explicit iterator usage.

So, you should use the enhanced for loop by default, but consider a hand-written counted loop for performance-critical ArrayList iteration.

You're using an ArrayList, so the results you're getting seem fairly consistent with this statement.