Permission (guard blocks) vs. Forgiveness (catching NPEs)

PermissionVsForgiveness.java

import java.util.Arrays;
import java.util.Random;
import java.util.concurrent.Callable;

public class PermissionVsForgiveness {

    int[] a1, a2, a3, a4;

    Callable<Integer> permission = new Callable<Integer>() {
        public Integer call() throws Exception {
            if (a1 == null || a2 == null || a3 == null || a4 == null) return 0;
            return a1[0] + a2[0] + a3[0] + a4[0];

        }
    };

    Callable<Integer> forgiveness = new Callable<Integer>() {
        public Integer call() throws Exception {
            try {
                return a1[0] + a2[0] + a3[0] + a4[0];
            } catch (NullPointerException npe) {
                return 0;
            }
        }
    };

    Callable<Integer> ignorance = new Callable<Integer>() {
        public Integer call() throws Exception {
            return 0;
        }
    };

    public static void main(String args[]) {
        try {
            new PermissionVsForgiveness().calculate(100);
            System.out.println();
            new PermissionVsForgiveness().calculate(10000);
            System.out.println();
            new PermissionVsForgiveness().calculate(1000000);
        } catch (Exception e) {
            System.out.println("oopsies!");
            e.printStackTrace();
        }
    }


    public void calculate(int iterations) throws Exception {
        Random rand = new Random();

        for (Callable<Integer> notALambda : Arrays.asList(permission, forgiveness, ignorance)) {
            for (int fraction = 1; fraction < 20; fraction++) {
                double frequency = 1.0 / (1 << fraction);
                int foolHotspot = 0;
                long start = System.currentTimeMillis();
                for (int i = 0; i < iterations; i++) {
                    a1 = new int[]{i};
                    a2 = new int[]{i};
                    a3 = new int[]{i};
                    a4 = new int[]{i};
                    if (rand.nextDouble() < frequency) {
                        a1 = null;
                        a2 = null;
                        a3 = null;
                        a4 = null;
                    }
                    foolHotspot += notALambda.call();
                }
                long end = System.currentTimeMillis();
                System.gc();
                System.gc();
                System.gc();
                if (foolHotspot * start == end) System.out.println("Whodathough");
                System.out.println(
                        String.format("%f%% %fms",
                                frequency * 100, ((end - start) / ((double) iterations)) * 1000));
            }
            System.out.println();
        }
    }
}