Performance comparison of iteration vs steams

perf_iteration_vs_streams.java

import org.jetbrains.annotations.NotNull;

import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Function;
import java.util.stream.Collectors;

public class Solution {
    public static void main(String[] args) {
        String str = "Basic Service Set (BSS): A set of stations controlled by a single coordination function.\n" +
                "Distribution: The service that, by using association information,\n" +
                "delivers medium access control (MAC) service data units (MSDUs)\n" +
                "within the distribution system (DS).\n" +
                "Distribution System Service (DSS): The set of services provided by\n" +
                "(MAC) layer to transport MAC service data units (MSDUs) between\n" +
                "stations that are not in direct communication with each other over a\n" +
                "single instance of the wireless medium (WM).  These services include\n" +
                "the transport of MSDUs between the access points (APs) of basic\n" +
                "service sets (BSSs) within an extended service set (ESS), transport\n" +
                "of MSDUs between portals and BSSs within an ESS, and transport of\n" +
                "MSDUs between stations in the same BSS in cases where the MSDU has a\n" +
                "multicast or broadcast destination address, or where the destination\n" +
                "is an individual address but the station sending the MSDU chooses to\n" +
                "involve the DSS.  DSSs are provided between pairs of IEEE 802.11\n" +
                "MACs.\n" +
                "Integration: The service that enables delivery of medium access\n" +
                "control (MAC) service data units (MSDUs) between the distribution\n" +
                "system (DS) and an existing, non-IEEE 802.11 local area network (via\n" +
                "a portal).\n" +
                "Station (STA): A device that contains an IEEE 802.11 conformant\n" +
                "medium access control (MAC) and physical layer (PHY) interface to the\n" +
                "wireless medium (WM).\n" +
                "Portal: The logical point at which medium access control (MAC)\n" +
                "service data units (MSDUs) from a non-IEEE 802.11 local area network\n" +
                "(LAN) enter the distribution system (DS) of an extended service set\n" +
                "(ESS).\n" +
                "WLAN: In this document, WLAN refers to a logical component\n" +
                "instantiated on a WTP device.  A single physical WTP may operate a\n" +
                "number of WLANs.  Each Basic Service Set Identifier (BSSID) and its\n" +
                "constituent wireless terminal radios is denoted as a distinct WLAN on\n" +
                "a physical WTP.\n" +
                "Wireless Termination Point (WTP): The physical or network entity that\n" +
                "contains an IEEE 802.11 RF antenna and wireless PHY to transmit and\n" +
                "receive station traffic for wireless access networks.";
        long start = System.nanoTime();
        Set<Character> characterList = getDuplicateCharsSetIterative(str);
        long end = System.nanoTime();
        long execution = end - start;
        System.out.println("Execution time is " + execution + " nanoseconds");
        System.out.println(characterList);
        /*
        Execution time is 1011943 nanoseconds
                [
        ,  , (, ), ,, -, ., 0, 1, 2, 8, :, A, B, C, D, E, H, I, L, M, N, P, S, T, U, W, Y, a, b, c, d, e, f, g, h, i, k, l, m, n, o, p, r, s, t, u, v, w, x, y]
        */

        start = System.nanoTime();
        Set<Character> duplicateCharsSet = getDuplicateCharsSetStreams(str);
        end = System.nanoTime();
        execution = end - start;
        System.out.println("Execution time is " + execution + " nanoseconds");
        System.out.println(duplicateCharsSet);
        /*
        Execution time is 9840996 nanoseconds
                [
        ,  , (, ), ,, -, ., 0, 1, 2, 8, :, A, B, C, D, E, H, I, L, M, N, P, S, T, U, W, Y, a, b, c, d, e, f, g, h, i, k, l, m, n, o, p, r, s, t, u, v, w, x, y]
        */
    }

    private static Set<Character> getDuplicateCharsSetIterative(String str) {
        int[] intArray = new int[256];
        Set<Character> characterSet = new HashSet<>();
        for (char ch : str.toCharArray()) {
            if (intArray[ch] > 0) {
                characterSet.add(ch);
            } else {
                intArray[ch] = 1;
            }
        }
        return characterSet;
    }

    @NotNull
    private static Set<Character> getDuplicateCharsSetStreams(String str) {
        return str
                .chars()
                .mapToObj(value -> (char) value)
                .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()))
                .entrySet()
                .stream()
                .filter(characterLongEntry -> characterLongEntry.getValue() > 1)
                .map(Map.Entry::getKey)
                .collect(Collectors.toSet());
    }
}