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Java Archives - Custom Web Application Developers in Bromley, London

Installing ChromeDriver for WebDriver – For the Techies (Java)

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If your using Webdriver to automate your web testing you’ll already know what a great tool it is.

This is a quick note on installing ChromeDriver for WebDriver (to test using the Chrome Browser).

1. get the latest version of chrome driver from this url http://chromedriver.storage.googleapis.com/index.html

2. unzip this and place it whenever you want

3. next in your java code tell it where to find the unzipped file (replace ‘path goes here’ with your location). And thats it job done ūüôā

System.setProperty(“webdriver.chrome.driver”,¬†¬† ¬† “/path goes here/chromedriver”);¬†

driver = new ChromeDriver(); 

 

I highly recommend installing ChromeDriver for WebDriver , especially if your only using one type of browser for your testing. Hopefully you found this useful.

Java Generics (2008)

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Notes on SCJP I did in 2008

Generics

 

Straight forward Type Safe Collections

 

List<Animal> myList = new ArrayList<Animal>();

 

the generic type in the declaration must match on both side of = , in this case <String>

(unless a wildcard is used to the left of the equals OR the ref has no gen type eg List myList).

 

can only add <Animal> or subtypes to myList

eg

 

myList.add(new Animal()); // GOOD

myList.add(new Dog()); // GOOD

 

myList.add(new Integer()); //ERROR

 

Passing / Returning from method

void myMeth(List<Animal> animals){ …

 

can accept

List<Animal>, Vector<Animal> // GOOD

 

cannot accept

List<Dog>, ArrayLis<Cat> // ERROR

 

 

Mixing Old and New Collections

List<Integer> list = new ArrayList<Integer>();

 

oldClass.alterList(list)

class OldClass{

    void alterList(List List){

¬†¬†¬†¬†¬†¬†¬†list.add(” a string ! “); // works

   }

} 

 

Its not until someone calls a Integer method on the String obj in the collection that it will blow up ! 

However the compiler will issue a warning.

 

 

Type Safe Collections with wildcards

When you dont need to add to a collection

void lookAtThis(List<? extends Animal>){ …

 

can take:

 

List<Animal>

ArrayList<Dog>

Vector<Lion>

etc

 

can also take class type that implements an interface. [eg Animal implements ManEater]

 

List<? extends Animal> li = new ArrayList<Dog>(); // GOOD

this means assign anything to li that is Animal or subclass BUT will not be able to add to it

 

List<?> list is equivalent to : List<? extends Object>

 

Wildcards when you need to add to a collection 

void addTo(List<? super Dog> list){ …

 

this can take:

 

List<Dog>

List<Animal>

List<Object>

 

adding to:

 

list.add(new Dog()); // GOOD

 

list.add(new Object()); // ERROR

list.add(new Animal()); // ERROR

 

 

List<? super Dog> li = new ArrayList<Animal>(); // GOOD, looks abit weird usually more specific on right eg List l = new ArrayList();

li.add(new Animal()); // ERROR weird but true

li.add(new Alsatian()); // GOOD

 

Summary:

When see a ref that has notation like List<?> this can take list of any type but cannot add to it.

 

Generic Type Reference Task is task valid? Notes
 
List<Animal> list list.add(new Dog()); Y OK add

NOT OK poly pass list type

pass this to it List <Dog> N
list.add(new Animal()); Y
 
List<? extends Animal> list list.add(anything); N OK pass poly generic subtypes

CAN NOT add to

pass ArrayList<Dog> Y
pass List<Alsatian> list Y
 
List<? super Dog> list list.add(new Dog()); Y OK pass generic supertype to it

OK ADD only the generic type to it

list.add(new Animal()); N
pass List<Dog> Y
pass List<Animal> Y

 

 

Templating your own Classes  

 A class can be templated (such as the collections classes have been in the API). Instance vars, method pass and return types can all be templated eg:

 

class GenExample<T>{

    T obj;

    List<T> myList;

 

    void meth1(T var){

       this.obj = var;

    }

 

    List<T> getList(){

       return myList;

    }

 

    T getObj(){

       return obj;

    }

}

 

if the class above was instantiated as  GenExample<String> eg = new GenExample<String>();

it would produce an instan ce of the class below. 

 

class GenExample<String>{

    String obj;

    List<String> myList;

 

    void meth1(String var){

       this.obj = var;

    }

 

    List<String> getList(){

       return myList;

    }

 

    String getObj(){

       return obj;

    }

}

 

Templating your own Methods 

 if you done need to template a whole class you could just template one method eg

 

public <T> void aMethod(T obj){ ….

 

here the template type MUST come before anything else including the return type.

 

For both class and methods you can put boundaries on them e.g.

 

public <T extends CharSequence> void aMethod(T obj){ ….

 

note the syntax is slightly different to that used when declaring a generice reference to something e.g. List<? extends Object> list