Sample Code: 

public  class  A  
{
    public void m1(int ... i)
    {
        System.out.println("Parent class");
    }
}

public class B extends A
{
    public void m1(int i)
    {
        System.out.println("child class");
	}
}

class C
{
    public static void main(String[] args)
    {
        A a = new A();
        a.m1(10);

        B b=new B();
        b.m1(10);

        A a1=new B();
        a1.m1(10);
    }
}

Output:

Parent class

child class

Parent class

Use below code:

driver.getCurrentUrl();

Use below code:

driver.navigate().back();
driver.navigate().forward();

If that menu has been created by using select tag then we can use the methods selectByValue() or selectByIndex() or selectByVisibleText(). These are the methods of the Select class.

If the menu has not been created by using the select tag then we can simply find the xpath of that element and click on that to select.

Check below code:

WebDriver frame(int index);
WebDriver frame(String nameOrId);
WebDriver frame(WebElement frameElement);

Use Action Class:

Actions act = new Actions(driver);
WebElement source = driver.findElement(By.xpath("")); //source element which you want to drag
WebElement target = driver.findElement(By.xpath("")); //target where you want to drop
act.dragAndDrop(source, target).perform();

Use Below code:

Actions act = new Actions(driver); 
act.moveToElement(webElement).perform();
act.contextClick().perform();

Check below code:

WebDriver driver;

if(browser.equals("Chrome"))
{	
    System.setProperty("webdriver.chrome.driver", Constants.CHROME_EXE);
    driver = new ChromeDriver();
}
else if(browser.equals("Firefox")) 
{
    System.setProperty("webdriver.gecko.driver", Constants.FIREFOX_EXE);
    driver = new FirefoxDriver();
}
else if(browser.equals("IE"))
{
    System.setProperty("webdriver.ie.driver","Constants.IE_EXE");
    driver = new InternetExplorerDriver();
}

To handle alert pop-ups, we need to 1st switch control to alert then click on ok or cancel then move control back to main page.

String mainPage = driver.getWindowHandle();

Alert alt = driver.switchTo().alert(); // to move control to alert popup
alt.accept(); // to click on ok.
alt.dismiss(); // to click on cancel.

//Then move the control back to main web page
driver.switchTo().window(mainPage);

use submit() method but it can be used only when attribute type=submit.

You can also use JavaScriptExecutor, Keys.Enter or Action class to click on button.