<dependency>
    <groupId>com.github.houbb</groupId>
    <artifactId>junitperf</artifactId>
    <version>2.0.0</version>
</dependency>

import com.github.houbb.junitperf.core.annotation.JunitPerfConfig;
import com.github.houbb.junitperf.core.report.impl.HtmlReporter;
import org.junit.jupiter.api.BeforeAll;
import java.util.Arrays;
import java.util.Random;
public class StreamIntTest {
    public static int[] arr;
    @BeforeAll
    public static void init() {
        arr = new int[500000000];  //5億個隨機Int
        randomInt(arr);
    }
    @JunitPerfConfig( warmUp = 1000, reporter = {HtmlReporter.class})
    public void testIntFor() {
        minIntFor(arr);
    }
    @JunitPerfConfig( warmUp = 1000, reporter = {HtmlReporter.class})
    public void testIntParallelStream() {
        minIntParallelStream(arr);
    }
    @JunitPerfConfig( warmUp = 1000, reporter = {HtmlReporter.class})
    public void testIntStream() {
        minIntStream(arr);
    }
    private int minIntStream(int[] arr) {
        return Arrays.stream(arr).min().getAsInt();
    }
    private int minIntParallelStream(int[] arr) {
        return Arrays.stream(arr).parallel().min().getAsInt();
    }
    private int minIntFor(int[] arr) {
        int min = Integer.MAX_VALUE;
        for (int anArr : arr) {
            if (anArr < min) {
                min = anArr;
            }
        }
        return min;
    }
    private static void randomInt(int[] arr) {
        Random r = new Random();
        for (int i = 0; i < arr.length; i++) {
            arr[i] = r.nextInt();
        }
    }
}

import com.github.houbb.junitperf.core.annotation.JunitPerfConfig;
import com.github.houbb.junitperf.core.report.impl.HtmlReporter;
import org.junit.jupiter.api.BeforeAll;
import java.util.ArrayList;
import java.util.Random;
public class StreamStringTest {
    public static ArrayList<String> list;
    @BeforeAll
    public static void init() {
        list = randomStringList(1000000);
    }
    @JunitPerfConfig(duration = 10000, warmUp = 1000, reporter = {HtmlReporter.class})
    public void testMinStringForLoop(){
        String minStr = null;
        boolean first = true;
        for(String str : list){
            if(first){
                first = false;
                minStr = str;
            }
            if(minStr.compareTo(str)>0){
                minStr = str;
            }
        }
    }
    @JunitPerfConfig(duration = 10000, warmUp = 1000, reporter = {HtmlReporter.class})
    public void textMinStringStream(){
        list.stream().min(String::compareTo).get();
    }
    @JunitPerfConfig(duration = 10000, warmUp = 1000, reporter = {HtmlReporter.class})
    public void testMinStringParallelStream(){
        list.stream().parallel().min(String::compareTo).get();
    }
    private static ArrayList<String> randomStringList(int listLength){
        ArrayList<String> list = new ArrayList<>(listLength);
        Random rand = new Random();
        int strLength = 10;
        StringBuilder buf = new StringBuilder(strLength);
        for(int i=0; i<listLength; i++){
            buf.delete(0, buf.length());
            for(int j=0; j<strLength; j++){
                buf.append((char)('a'+ rand.nextInt(26)));
            }
            list.add(buf.toString());
        }
        return list;
    }
}

import com.github.houbb.junitperf.core.annotation.JunitPerfConfig;
import com.github.houbb.junitperf.core.report.impl.HtmlReporter;
import org.junit.jupiter.api.BeforeAll;
import java.util.*;
import java.util.stream.Collectors;
public class StreamObjectTest {
    public static List<Order> orders;
    @BeforeAll
    public static void init() {
        orders = Order.genOrders(10);
    }
    @JunitPerfConfig(duration = 10000, warmUp = 1000, reporter = {HtmlReporter.class})
    public void testSumOrderForLoop(){
        Map<String, Double> map = new HashMap<>();
        for(Order od : orders){
            String userName = od.getUserName();
            Double v; 
            if((v=map.get(userName)) != null){
                map.put(userName, v+od.getPrice());
            }else{
                map.put(userName, od.getPrice());
            }
        }
    }
    @JunitPerfConfig(duration = 10000, warmUp = 1000, reporter = {HtmlReporter.class})
    public void testSumOrderStream(){
        orders.stream().collect(
                Collectors.groupingBy(Order::getUserName, 
                        Collectors.summingDouble(Order::getPrice)));
    }
    @JunitPerfConfig(duration = 10000, warmUp = 1000, reporter = {HtmlReporter.class})
    public void testSumOrderParallelStream(){
        orders.parallelStream().collect(
                Collectors.groupingBy(Order::getUserName, 
                        Collectors.summingDouble(Order::getPrice)));
    }
}
class Order{
    private String userName;
    private double price;
    private long timestamp;
    public Order(String userName, double price, long timestamp) {
        this.userName = userName;
        this.price = price;
        this.timestamp = timestamp;
    }
    public String getUserName() {
        return userName;
    }
    public double getPrice() {
        return price;
    }
    public long getTimestamp() {
        return timestamp;
    }
    public static List<Order> genOrders(int listLength){
        ArrayList<Order> list = new ArrayList<>(listLength);
        Random rand = new Random();
        int users = listLength/200;// 200 orders per user
        users = users==0 ? listLength : users;
        ArrayList<String> userNames = new ArrayList<>(users);
        for(int i=0; i<users; i++){
            userNames.add(UUID.randomUUID().toString());
        }
        for(int i=0; i<listLength; i++){
            double price = rand.nextInt(1000);
            String userName = userNames.get(rand.nextInt(users));
            list.add(new Order(userName, price, System.nanoTime()));
        }
        return list;
    }
    @Override
    public String toString(){
        return userName + "::" + price;
    }
}