Testing parrallel vs serial filtering in Java8

ParrallelTest.java

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

/**
 * Created by wouter on 19-03-14.
 */
public class ParrallelTest {

    public static final int SET_SIZE = 1000000;

    @org.junit.Test
    public void testParallelStream() throws Exception {

        Random random = new Random();

        System.out.println("Filtering " + SET_SIZE + " items...");

        long timeForSerialFilter = testSerialFilter(random);
        System.out.println("Time for Serial filter = " + timeForSerialFilter + "ms.");

        long timeForParallelFilter = testParallelFilter(random);
        System.out.println("Time for Parallel filter = " + timeForParallelFilter + "ms.");

    }

    private long testSerialFilter(final Random random) {
        List<Data> data1 = new ArrayList<>(SET_SIZE);
        for (int i = 0 ; i < SET_SIZE ; i++) {
            data1.add(new Data(random.nextBoolean()));
        }

        long start = System.currentTimeMillis();

        data1.stream().filter(it -> it.successful).count();

        return System.currentTimeMillis() - start;
    }

    private long testParallelFilter(final Random random) {
        final long start;List<Data> data2 = new ArrayList<>(SET_SIZE);
        for (int i = 0 ; i < SET_SIZE ; i++) {
            data2.add(new Data(random.nextBoolean()));
        }

        start = System.currentTimeMillis();

        data2.parallelStream().filter(it -> it.successful).count();

        return System.currentTimeMillis() - start;
    }

    private class Data {

        final boolean successful;

        private Data(final boolean successful) {
            this.successful = successful;
        }
    }
}