ArrayList vs. LinkedList

ListsBenchmark.java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.function.Supplier;

public class ListsBenchmark {

    private static final int UPTO = 1 << 24;
    private static final Object ELEMENT = new Object();

    private static final int TRIALS_WARMUP = 5;
    private static final int TRIALS_REAL = 10;

    private static long runBenchmarkFor(Supplier<List<Object>> creator) {
        List<Object> target = creator.get();
        long start = System.nanoTime();
        for (int i = 0; i < UPTO; i++) {
            target.add(ELEMENT);
        }
        Iterator<Object> it = target.iterator();
        while (it.hasNext()) {
            it.next();
        }
        long end = System.nanoTime();
        return end - start;
    }

    private static class BenchmarkCase {
        public final String name;
        public final Supplier<List<Object>> producer;

        public BenchmarkCase(String name, Supplier<List<Object>> impl) {
            super();
            this.name = name;
            this.producer = impl;
        }
    }

    public static void main(String[] args) {
        final List<BenchmarkCase> impls = Arrays.asList(
                new BenchmarkCase("ArrayList", ArrayList::new),
                new BenchmarkCase("LinkedList", LinkedList::new));

        System.out.print("Warming up the JVM");
        for (int i = 0; i < TRIALS_WARMUP; i++) {
            for (BenchmarkCase impl : impls) {
                runBenchmarkFor(impl.producer);
            }
            System.out.print(".");
            System.out.flush();
        }
        System.out.println();

        final Map<BenchmarkCase, Long> results = new HashMap<>();
        System.out.println("Running trials: ");
        for (int i = 1; i <= TRIALS_REAL; i++) {
            for (BenchmarkCase impl : impls) {
                results.merge(impl, runBenchmarkFor(impl.producer),
                        (a, b) -> a + b);
                System.gc();
            }
            System.out.print(i);
            System.out.print(" ");
            System.out.flush();
        }
        System.out.println();
        System.out.println();

        System.out.println("Results (total time):");
        for (Map.Entry<BenchmarkCase, Long> result : results.entrySet()) {
            long time = result.getValue();
            System.out.format("%s: %d ns (%.03f s)%n", result.getKey().name,
                    time, time / 1e9);
        }
    }

}