[Java] Iteratorと配列の処理時刻比較

概要

Javaにおいて，Iteratorと配列に対して，それぞれシーケンシャルにアクセスした場合の処理時間を比較しました．

コード

main.java

import java.util.Iterator;
import java.util.Arrays;
import java.util.ArrayList;


public class main {
    public static void main(String[] args) {
        long t1,t2,t3;
        int l = 100000000;
        long procTimeArray, procTimeIter;
        int counter1 = 0,counter2 = 0;
        Object temp;
        Integer [] array = new Integer [l];
        System.out.println("Array  / Iterator (ms)");
        System.out.println("----------------");

        for(int trial = 0; trial < 10; trial++){
            Iterator it = new ArrayList<Integer>(Arrays.asList(array)).iterator();
            t1 = System.currentTimeMillis();
            for ( int i = 0; i < l; i++ ){
                temp = array[i];
            }
            t2 = System.currentTimeMillis();
            while ( it.hasNext() ){
                temp = it.next();
            }
            t3 = System.currentTimeMillis();

            procTimeIter = (t3 - t2);
            procTimeArray = (t2 - t1);
            System.out.println(procTimeArray+" / "+procTimeIter);
            counter1 += procTimeArray;
            counter2 += procTimeIter;
        }
        System.out.println("----------------");
        System.out.println("Average:" + (int)counter1/10+" / "+(int)counter2/10);
    }

}

結果

Array  / Iterator (ms)
----------------
7 / 19
27 / 18
0 / 16
0 / 14
0 / 14
0 / 14
0 / 14
0 / 14
0 / 19
0 / 14
----------------
Average:3 / 15