ArrayList処理と配列処理の実行時間の比較。

Main.java

public class Main {
    private final int quantity = 1000000;
    // frequencyの値を増やすほど精度が増す。
    private final int frequency = 10;
    // コンストラクタで要素数指定。
    private final List<Integer> list = new ArrayList<>(quantity);
    private final int[] array = new int[quantity];

    public static void main(String[] args) {
        Main main = new Main();
        List<Long> arrayMeanValue = new ArrayList<>();
        List<Long> arrayListMeanValue = new ArrayList<>();

        System.out.println("要素数" + main.quantity + "で処理を開始します。");
        for (int i = 0; i < main.frequency; i++) {
            System.out.println("配列処理(" + i + 1 + "回目)を開始します。");
            long executionTimeArray = main.measureTime(main::useArray, main.quantity);
            System.out.println("終了しました。");
            arrayMeanValue.add(executionTimeArray);

            System.out.println("ArrayList処理(" + i + 1 + "回目)を開始します。");
            long executionTimeList = main.measureTime(main::useArrayList, main.quantity);
            System.out.println("終了しました。");
            arrayListMeanValue.add(executionTimeList);
        }

        long arrayMeanValueAve = main.calcAverage(arrayMeanValue);
        long arrayListMeanValueAve = main.calcAverage(arrayListMeanValue);

        System.out.println("配列処理の実行平均時間:" + arrayMeanValueAve/ 1000000 + "ms");
        System.out.println("ArrayList処理の実行時間:" + arrayListMeanValueAve / 1000000 + "ms");

        System.out.println("配列処理のほうが" + main.compareValue(arrayMeanValueAve, arrayListMeanValueAve) / 1000000 + "ms速いです。");
    }

    private void useArray(int quantity) {
        for (int i = 0; i < quantity; i++) {
            array[i] = i;
        }
        Arrays.stream(array).forEach(System.out::println);
        Arrays.fill(array, 0);
    }

    private void useArrayList(int quantity) {
        for (int i = 0; i < quantity; i++) {
            list.add(i);
        }
        list.stream().forEach(System.out::println);
        list.clear();
    }

    private long calcAverage(List<Long> list) {
        long sum = 0;
        for (long value : list) {
            sum += value;
        }
        return sum / list.size();
    }

    private long compareValue(long a, long b) {
        return a - b;
    }

    private <T> long measureTime(Consumer<T> proc, T arg) {
        long start = System.nanoTime();
        proc.accept(arg);
        return System.nanoTime() - start;
    }
}