how expensive are exceptions in java? why should they be exceptional?

Test.java

import java.util.List;
import java.util.ArrayList;

public class Test {
    public static void main(String [] args) {
        int numIterations = Integer.parseInt(args[0]);
        int totalS = Integer.parseInt(args[1]);
        int numFoo = Integer.parseInt(args[2]);

        //String [] s = { "not foo", "foo", "foo", "not foo", "more not foo", "long string that is most definitely not foo", "short", "more strings", "foo", "foo", "there's a lot of foo here", "foo", "foo", "foo"};
        //String [] initialS = { "not foo", "not foo", "more not foo", "long string that is most definitely not foo", "short", "more strings", "there's a lot of foo here", "eight", "nine", "ten" };

        List<String> listOfStrings = new ArrayList<String>();

        for(int i=0; i < totalS - numFoo; i++) {
            listOfStrings.add("not foo");
        }

        for(int i=0; i<numFoo; i++) {
            listOfStrings.add("foo");
        }

        String[] s = new String[listOfStrings.size()];
        s = listOfStrings.toArray(s);

        long start = System.currentTimeMillis();
        for(int i=0; i < Integer.parseInt(args[0]); i++) {
            testExceptions(s);
        }

        System.out.println("exceptions took " + (System.currentTimeMillis() - start) + " for "+(totalS*numIterations)+" iterations");

        start = System.currentTimeMillis();
        for(int i=0; i < Integer.parseInt(args[0]); i++) {
            testControlStructures(s);
        }

        System.out.println("constrol structures took " + (System.currentTimeMillis() - start) + " for "+(totalS*numIterations)+" iterations");
    }

    private static void testExceptions(String [] s) {
        int totalLength = 0;
        for (int i=0; i < s.length; i++) {
            try {
                totalLength += processString(s[i]);
            } catch (IllegalArgumentException e) {
                //no-op
            }
        }
    }

    private static void testControlStructures(String [] s) {
        int totalLength = 0;
        for (int i=0; i < s.length; i++) {
            if(null != s && !("foo".equals(s[i]))) {
                totalLength += processString(s[i]);
            }
        }
    }

    private static int processString(String s) {
        if (null == s) {
            throw new IllegalArgumentException("null is not allowed!");
        }

        if ("foo".equals(s)) {
            throw new IllegalArgumentException("foo is not allowed!");
        }

        return s.length();
    }
}