GetMetrics.java

package com.devtools;

import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.devtools.DevTools;
import org.openqa.selenium.devtools.performance.Performance;
import org.openqa.selenium.devtools.performance.model.Metric;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class GetMetrics {

    final static String PROJECT_PATH = System.getProperty("user.dir");

    public static void main(String[] args){
        System.setProperty("webdriver.chrome.driver", PROJECT_PATH + "/src/main/resources/chromedriver");
        ChromeDriver driver = new ChromeDriver();
        DevTools devTools = driver.getDevTools();
        devTools.createSession();
        devTools.send(Performance.enable());

        driver.get("https://www.google.org");

        List<Metric> metrics = devTools.send(Performance.getMetrics());
        List<String> metricNames = metrics.stream()
                .map(o -> o.getName())
                .collect(Collectors.toList());

        devTools.send(Performance.disable());

        List<String> metricsToCheck = Arrays.asList(
                "Timestamp", "Documents", "Frames", "JSEventListeners",
                "LayoutObjects", "MediaKeySessions", "Nodes",
                "Resources", "DomContentLoaded", "NavigationStart");

        metricsToCheck.forEach( metric -> System.out.println(metric +
                " is : " + metrics.get(metricNames.indexOf(metric)).getValue()));
    }
}