小さめのサイズでArrayとArrayListの速度比較を行ってみました。
[前提]
・サイズは 10-100 程度
・リストの容量と中身の大きさはほぼ同じ
・用途は、更新頻度が高いイベントの配布先の管理に使う
[結果]
Arrayのforとforeachはほぼ同じ。
ArrayListでも通常のforループで回すと余り変わらない 。若干ArrayListが遅いか。
foreach、streamは遅い。foreachで2倍程度。
[Array - for]
Start : 1406987147093, End : 1406987147102, Took : 9
[Array - foreach]
Start : 1406987147122, End : 1406987147131, Took : 9
[ArrayList - for]
Start : 1406987147132, End : 1406987147142, Took : 10
[ArrayList - foreach]
Start : 1406987147142, End : 1406987147174, Took : 32
[ArrayList - stream]
Start : 1406987147174, End : 1406987147229, Took : 55
※初期容量を非常に大きくした場合
⇒foreachが大きく影響を受ける。
[Array - for]
Start : 1406987109799, End : 1406987109809, Took : 10
[Array - foreach]
Start : 1406987109826, End : 1406987109835, Took : 9
[ArrayList - for]
Start : 1406987109835, End : 1406987109845, Took : 10
[ArrayList - foreach]
Start : 1406987109845, End : 1406987110117, Took : 272
[ArrayList - stream]
Start : 1406987110118, End : 1406987110526, Took : 408
import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class ListAndArray {
private final int SIZE = 20;
private final int OUTER_COUNT = 100000;
private ExecutorService executer = Executors.newFixedThreadPool(SIZE);
public static void main(String[] args) {
ListAndArray instance = new ListAndArray();
instance.calcListVsArray();
}
public void calcListVsArray() {
// initialize
List list = new ArrayList<>(SIZE);
for (int i = 0; i < SIZE; i++) {
list.add(new EventListenerSample());
}
EventListenerSample[] array = list.toArray(new EventListenerSample[list.size()]);
long startTime;
long endTime;
long miliExecTime;
// calc
System.out.println("[Array - for]");
startTime = System.currentTimeMillis();
for (int outer = 0; outer < OUTER_COUNT; outer++) {
for (int i = 0; i < SIZE; i++) {
array[i].getLocalDateTime();
}
}
endTime = System.currentTimeMillis();
miliExecTime = endTime - startTime;
System.out.printf("Start : %d, End : %d, Took : %d %n", startTime, endTime, miliExecTime);
System.out.println("[Array - foreach]");
startTime = System.currentTimeMillis();
for (int outer = 0; outer < OUTER_COUNT; outer++) {
for (EventListenerSample eventListenerSample : array) {
eventListenerSample.getLocalDateTime();
}
}
endTime = System.currentTimeMillis();
miliExecTime = endTime - startTime;
System.out.printf("Start : %d, End : %d, Took : %d %n", startTime, endTime, miliExecTime);
System.out.println("[ArrayList - for]");
startTime = System.currentTimeMillis();
for (int outer = 0; outer < OUTER_COUNT; outer++) {
for (int i = 0; i < SIZE; i++) {
list.get(i).getLocalDateTime();
}
}
endTime = System.currentTimeMillis();
miliExecTime = endTime - startTime;
System.out.printf("Start : %d, End : %d, Took : %d %n", startTime, endTime, miliExecTime);
System.out.println("[ArrayList - foreach]");
startTime = System.currentTimeMillis();
for (int outer = 0; outer < OUTER_COUNT; outer++) {
for (EventListenerSample eventListenerSample : list) {
eventListenerSample.getLocalDateTime();
}
}
endTime = System.currentTimeMillis();
miliExecTime = endTime - startTime;
System.out.printf("Start : %d, End : %d, Took : %d %n", startTime, endTime, miliExecTime);
System.out.println("[ArrayList - stream]");
startTime = System.currentTimeMillis();
for (int outer = 0; outer < OUTER_COUNT; outer++) {
list.stream().forEach(e -> e.getLocalDateTime());
}
endTime = System.currentTimeMillis();
miliExecTime = endTime - startTime;
System.out.printf("Start : %d, End : %d, Took : %d %n", startTime, endTime, miliExecTime);
}
public static class EventListenerSample {
private Integer integer = Integer.MAX_VALUE - 1;
private String b = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";
private String c = "ccccccccccccccccccccccccccccccc";
private LocalDateTime localDateTime = LocalDateTime.now();
public LocalDateTime getLocalDateTime() {
return localDateTime;
}
}
}
