在使用Selenium webdriver时，为什么我们使用链表来收集链接或下拉内容与mutliple匹配？

Question

Example code is something like this, (this was an interview question asked for me recently)

List linkElements = driver.findElements(By.tagName("a"));

Answer 1

I would say, through List you can dynamically add, access and remove objects of the same type. Also, it won't mind even if it has No contents.

Generally you choose a Data Structure according to your needs. Here while doing a findElements() search we are saying that we want all the elements with the given structure in DOM and we can't be always sure about it's size in advance. Using a fixed sized array in such conditions won't make much sense.

I hope it helps :)

Answer 2

List represents an ordered list of objects, meaning you can access the elements of a List in a specific order, and by an index too. You can also add the same element more than once to a List. List allows null elements and you can have many null objects in a List

You will get all the result in a particular order one by one. It is also allow you to add duplicates. Our result can have duplicates which mainly we need in automation , but if your requirement is different and you do not need duplicates then you can use other collection type.If you use set then it will not allow duplicates and it's an unorder presentation of object.

We use List because when we are using findElements() instead of findElement() then we are expecting that locator will return us more than 1 element(Not in every case or scenario). So it's a good practice to use List so our data is saved in list in a ordered manner so we can use them properly.

Generally I am using List in below manner:-

 List<WebElement> allOptions = dropDown.findElements(By."OUR Locator");
    for ( WebElement we: allOptions) { 
        dropDown.sendKeys( Keys.DOWN ); //simulate visual movement
        sleep(250);       
        if ( we.getText().contains( text ) ) select.selectByVisibleText("Value1");
    }

You can also do it in many ways refer below:-

https://sqa.stackexchange.com/questions/8029/how-to-iterate-a-list-of-webelements-and-print-the-values-one-by-one-to-perform

Here is more detail version which help you to identify that when to use list:-

http://java67.blogspot.in/2013/01/difference-between-set-list-and-map-in-java.html

Adding and Accessing Elements

To add elements to a List you call its add() method. This method is inherited from the Collection interface. Here are a few examples:

List listA = new ArrayList();

listA.add("element 1");
listA.add("element 2");
listA.add("element 3");

You can access them via index as below:-

String element0 = listA.get(0);
String element1 = listA.get(1);
String element3 = listA.get(2);

System.out.println(element0+" "+element1+" "+element3 );

Hope it will help you :)