使用Map优化双层For循环

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;

public class ForUpdate {

    public static void main(String[] args) {

//        for (int i = 0; i < 10000; i += 10) {
//            loopGivenNum(i);
//        }
        for (int i = 10000; i < 100000; i += 10000) {
            loopGivenNum(i);
        }
        System.out.println("----- done -----");

    }

    private static void loopGivenNum(int i) {
        List<String> smallLoop = getLoopList(i);
        List<String> bigLoop = getLoopList(2 * i);
        long doByForTimes = doByFor(bigLoop, smallLoop);
        long doByMapTimes = doByMap(bigLoop, smallLoop);
        System.out.println("size " + i + ": " + doByForTimes + "," + doByMapTimes);
    }

    /**
     * 获取循环变量
     * @param size 循环变量元素个数
     */
    private static List<String> getLoopList(int size) {
        List<String> list = new ArrayList<>();
        for (int i = 0; i < size; i++) {
            list.add(String.valueOf(i));
        }
        return list;
    }

    private static long doByFor(List<String> bigLoop, List<String> smallLoop) {
        long startTime = System.currentTimeMillis();
        for (String str1 : smallLoop) {
            for (String str2 : bigLoop) {
                if (str1.equals(str2)) {
                    continue;
                }
            }
        }
        return System.currentTimeMillis() - startTime;
    }

    /**
     * 使用 Map 优化
     * @param bigLoop
     * @param smallLoop
     */
    private static long doByMap(List<String> bigLoop, List<String> smallLoop) {
        long startTime = System.currentTimeMillis();
        // 转换成map
        Map<String, String> loopMap = bigLoop.stream().collect(Collectors.toMap(k -> k, Function.identity()));
        System.out.println(loopMap.size());
        for (String str1 : smallLoop) {
            if (loopMap.containsKey(str1)) {
                continue;
            }
        }
        return System.currentTimeMillis() - startTime;
    }
}

size 10000: 756,97
size 20000: 3091,8
size 30000: 4342,7
size 40000: 8848,7
size 50000: 16317,7
size 60000: 31652,7
size 70000: 37078,7