MegamorphicList.java

@State(Scope.Thread)
@OutputTimeUnit(TimeUnit.MICROSECONDS)
public class MegamorphicList {

    private List<String>[] strings;

    @Setup(Level.Trial)
    public void init() {
        strings = new List[]{getArrayList1(6), getArrayList2(6), getArrayList3(6), getArrayList(6), getFactoryList6(), getUnModifiableList(6)};
    }

    @Benchmark
    public int sumLength_ArrayList1() {
        List<String> list = strings[0];
        int blackhole = 0;
        for (int i = 0; i < list.size(); ++i) {
            blackhole += list.get(i).length();
        }
        return blackhole;
    }

    @Benchmark
    public int sumLength_ArrayList2() {
        List<String> list = strings[1];
        int blackhole = 0;
        for (int i = 0; i < list.size(); ++i) {
            blackhole += list.get(i).length();
        }
        return blackhole;
    }

    @Benchmark
    public int sumLength_ArrayList3() {
        List<String> list = strings[2];
        int blackhole = 0;
        for (int i = 0; i < list.size(); ++i) {
            blackhole += list.get(i).length();
        }
        return blackhole;
    }

    @Benchmark
    public int sumLength_ArrayList() {
        List<String> list = strings[3];
        int blackhole = 0;
        for (int i = 0; i < list.size(); ++i) {
            blackhole += list.get(i).length();
        }
        return blackhole;
    }

    @Benchmark
    public int sumLength_Factory() {
        List<String> list = strings[4];
        int blackhole = 0;
        for (int i = 0; i < list.size(); ++i) {
            blackhole += list.get(i).length();
        }
        return blackhole;
    }

    @Benchmark
    public int sumLength_Unmodifiable() {
        List<String> list = strings[5];
        int blackhole = 0;
        for (int i = 0; i < list.size(); ++i) {
            blackhole += list.get(i).length();
        }
        return blackhole;
    }

    @Benchmark
    public int sumLength_Random2() {
        List<String> list = strings[ThreadLocalRandom.current().nextInt(2)];
        int blackhole = 0;
        for (int i = 0; i < list.size(); ++i) {
            blackhole += list.get(i).length();
        }
        return blackhole;
    }

    @Benchmark
    public int sumLength_Random3() {
        List<String> list = strings[ThreadLocalRandom.current().nextInt(3)];
        int blackhole = 0;
        for (int i = 0; i < list.size(); ++i) {
            blackhole += list.get(i).length();
        }
        return blackhole;
    }

    @Benchmark
    public int sumLength_Random4() {
        List<String> list = strings[ThreadLocalRandom.current().nextInt(4)];
        int blackhole = 0;
        for (int i = 0; i < list.size(); ++i) {
            blackhole += list.get(i).length();
        }
        return blackhole;
    }

    @Benchmark
    public int sumLength_Random5() {
        List<String> list = strings[ThreadLocalRandom.current().nextInt(5)];
        int blackhole = 0;
        for (int i = 0; i < list.size(); ++i) {
            blackhole += list.get(i).length();
        }
        return blackhole;
    }

    @Benchmark
    public int sumLength_Random6() {
        List<String> list = strings[ThreadLocalRandom.current().nextInt(6)];
        int blackhole = 0;
        for (int i = 0; i < list.size(); ++i) {
            blackhole += list.get(i).length();
        }
        return blackhole;
    }

    private List<String> getUnModifiableList(int size) {
        return Collections.unmodifiableList(getArrayList(size));
    }

    private List<String> getFactoryList6() {
        return List.of(randomString(),
                randomString(),
                randomString(),
                randomString(),
                randomString(),
                randomString()
        );
    }

    private List<String> getArrayList(int size) {
        List<String> list = new ArrayList<>();
        for (int i = 0; i < size; ++i) {
            list.add(randomString());
        }
        return list;
    }

    private List<String> getArrayList1(int size) {
        List<String> list = new ArrayList1<>(); // copy of java.util.ArrayList which extends AbstractList1 which is a copy of java.util.AbstractList
        for (int i = 0; i < size; ++i) {
            list.add(randomString());
        }
        return list;
    }

    private List<String> getArrayList2(int size) {
        List<String> list = new ArrayList2<>(); // copy of java.util.ArrayList which extends AbstractList2 which is a copy of java.util.AbstractList
        for (int i = 0; i < size; ++i) {
            list.add(randomString());
        }
        return list;
    }

    private List<String> getArrayList3(int size) {
        List<String> list = new ArrayList3<>(); // copy of java.util.ArrayList which extends AbstractList3 which is a copy of java.util.AbstractList
        for (int i = 0; i < size; ++i) {
            list.add(randomString());
        }
        return list;
    }

    private String randomString() {
        return UUID.randomUUID().toString();
    }

}