Microbenchmark of `put()` and `get()` operations of Java Map implementations.

MapVsMap.java

import java.util.*;
import java.math.*;

public class MapVsMap {

    static final int MAP_SIZE = 100000;
    static final int STR_LEN = 10;
    static final int ROUNDS = 10;
    static final char[] chars = {
        'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
        'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 'A', 'B',
        'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
        'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '1', '2', '3', '4',
        '5', '6', '7', '8', '9', '0' 
    };

    static final Random random = new Random();

    static String randomString(int length) {
        StringBuilder s = new StringBuilder(length);
        for (int i = 0; i < length; i++) {
            s.append(chars[random.nextInt(chars.length)]);
        }
        return s.toString();
    }

    public static void main(String[] args) {
        LinkedList<String> strings = new LinkedList<String>();
        for (int i = 0; i < MAP_SIZE; i++) {
            strings.add(randomString(STR_LEN));
        }

        long start = 0;
        long end = 0;
        long elapsed = 0;
        long[] hput = new long[ROUNDS];
        long[] hget = new long[ROUNDS];
        long[] lput = new long[ROUNDS];
        long[] lget = new long[ROUNDS];
        long[] tput = new long[ROUNDS];
        long[] tget = new long[ROUNDS];

        for (int round = 0; round <= ROUNDS; round++) {
            System.out.println("\n\n=== ROUND " + round + " ===");
            HashMap<String, String> hm = new HashMap<String, String>();
            start = System.nanoTime();
            for (String string : strings) {
                hm.put(string, string);
            }
            end = System.nanoTime();
            elapsed = end - start;
            System.out.println("HashMap put: " + elapsed);
            if (round > 0) {
                hput[round - 1] = elapsed;
            }

            start = System.nanoTime();
            for (String string : strings) {
                hm.get(string);
            }
            end = System.nanoTime();
            elapsed = end - start;
            System.out.println("HashMap get: " + elapsed);
            if (round > 0) {
                hget[round - 1] = elapsed;
            }

            LinkedHashMap<String, String> lhm = new LinkedHashMap<String, String>();
            start = System.nanoTime();
            for (String string : strings) {
                lhm.put(string, string);
            }
            end = System.nanoTime();
            elapsed = end - start;
            System.out.println("LinkedHashMap put: " + elapsed);
            if (round > 0) {
                lput[round - 1] = elapsed;
            }

            start = System.nanoTime();
            for (String string : strings) {
                lhm.get(string);
            }
            end = System.nanoTime();
            elapsed = end - start;
            System.out.println("LinkedHashMap get: " + elapsed);
            if (round > 0) {
                lget[round - 1] = elapsed;
            }

            TreeMap<String, String> tm = new TreeMap<String, String>();
            start = System.nanoTime();
            for (String string : strings) {
                tm.put(string, string);
            }
            end = System.nanoTime();
            elapsed = end - start;
            System.out.println("TreeMap put: " + elapsed);
            if (round > 0) {
                tput[round - 1] = elapsed;
            }

            start = System.nanoTime();
            for (String string : strings) {
                tm.get(string);
            }
            end = System.nanoTime();
            elapsed = end - start;
            System.out.println("TreeMap get: " + elapsed);
            if (round > 0) {
                tget[round - 1] = elapsed;
            }
        }

        Arrays.sort(hput);
        Arrays.sort(hget);
        Arrays.sort(lput);
        Arrays.sort(lget);
        Arrays.sort(tput);
        Arrays.sort(tget);

        System.out.println("\n\n=== RESULTS (PUT) ===");
        System.out.format("HashMap PUT (%s rounds):\t min: %10s; max: %10s; ave: %10s%n",
                hput.length, hput[0], hput[hput.length - 1], ave(hput));
        System.out.format("LinkedHashMap PUT (%s rounds):\t min: %10s; max: %10s; ave: %10s%n",
                lput.length, lput[0], lput[lput.length - 1], ave(lput));
        System.out.format("TreeMap PUT (%s rounds):\t min: %10s; max: %10s; ave: %10s%n",
                tput.length, tput[0], tput[tput.length - 1], ave(tput));

        System.out.println("\n\n=== RESULTS (GET) ===");
        System.out.format("HashMap GET (%s rounds):\t min: %10s; max: %10s; ave: %10s%n",
                hget.length, hget[0], hget[hget.length - 1], ave(hget));
        System.out.format("LinkedHashMap GET (%s rounds):\t min: %10s; max: %10s; ave: %10s%n",
                lget.length, lget[0], lget[lget.length - 1], ave(lget));
        System.out.format("TreeMap GET (%s rounds):\t min: %10s; max: %10s; ave: %10s%n",
                tget.length, tget[0], tget[tget.length - 1], ave(tget));
    }

    static String ave(long[] times) {
        BigDecimal total = BigDecimal.ZERO;
        for (long time : times) {
            total = total.add(new BigDecimal(time));
        }
        return total.divide(new BigDecimal(times.length), MathContext.DECIMAL32).toPlainString();
    }
}