Why is iteration trough List<String> slower than split string and iterate over StringBuilder?

i was wondering why a List<String> for each loop is slower than a split for each on a StringBuilder

This is my code:

package nl.testing.startingpoint;

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

public class Main {

    public static void main(String args[]) {
        NumberFormat formatter = new DecimalFormat("#0.00000");

        List<String> a = new ArrayList<String>();
        StringBuffer b = new StringBuffer();        

        for (int i = 0;i <= 10000; i++)
        {
            a.add("String:" + i);
            b.append("String:" + i + " ");
        }

        long startTime = System.currentTimeMillis();
        for (String aInA : a) 
        {
            System.out.println(aInA);
        }
        long endTime   = System.currentTimeMillis();

        long startTimeB = System.currentTimeMillis();
        for (String part : b.toString().split(" ")) {

            System.out.println(part);
        }
        long endTimeB   = System.currentTimeMillis();

        System.out.println("Execution time from StringBuilder is " + formatter.format((endTimeB - startTimeB) / 1000d) + " seconds");
        System.out.println("Execution time List is " + formatter.format((endTime - startTime) / 1000d) + " seconds");

    }
}

The result is:

• Execution time from StringBuilder is 0,03300 seconds
• Execution time List is 0,06000 seconds

I would expect the StringBuilder to be slower because of the b.toString().split(" ")).

Can anyone explain this to me?