How do I launch the browser using Selenium WebDriver?

Here is the function to open either of Chrome or Firefox browser:

void openBrowser()
{
    if(browser.equals("Chrome"))
	{	
	    System.setProperty("webdriver.chrome.driver", Constants.CHROME_EXE);
	    ChromeOptions options = new ChromeOptions();
	    driver = new ChromeDriver(options);
	}
	else if(browser.equals("Firefox")) 
	{
	    System.setProperty("webdriver.gecko.driver", Constants.FIREFOX_EXE);
	    FirefoxOptions options = new FirefoxOptions();
            driver = new FirefoxDriver();
	}
        driver.get(url);
	
	driver.manage().window().maximize();
	driver.manage().timeouts().implicitlyWait(30, TimeUnit.SECONDS);	
}