Question

I have read some reference’s and i think i understood the usage the “new” keyword in OOP languange (but i don’t!)

So i can’t understand this line of code, i got it from the tut’s in thenewboston :

ourBrow = (WebView) findViewById(R.id.wvBrowser);
ourBrow.setWebViewClient(new OurViewClient());

So the setWebViewClient(); method requires a WebViewClient in it’s params. The think that i don’t understand is, why we need to add the “new” keyword here?
NOTE that OurViewClient() is a class that we made and extended by WebViewClient.

Sorry, if my way to ask the question is making you confuse, coz i also confuse now @_@

Thanks All! 😀

NOTE : English is not my native languange, so sorry if i made some mistake’s 😀

Answer 1

OurViewClient is the class that you made. OurViewClient() is a constructor for that class which takes 0 parameters. And the setWebViewClient() method requires a WebViewClient instance as its parameter.

So the new operator effectively allocates a new instance of the OurViewClient class and then invokes the default 0-parameter constructor on that instance, returning the created object. Using new is the only way you can create an instance of an Object in Java, barring more advanced topics like reflection or using things like sun.misc.Unsafe and also some exceptions centered around built-in types/autoboxing (e.g. String s = "str"; and Integer num = 7;).

Note that the following code is essentially equivalent to the code that you have:

WebViewClient client = new OurViewClient();
ourBrow = (WebView) findViewById(R.id.wvBrowser);
ourBrow.setWebViewClient(client);

Also note that the following are invalid:

WebViewClient client = OurViewClient();  //can't invoke a constructor without using 'new'
WebViewClient client = OurViewClient;    //can't assign the class
WebViewClient client;  //valid syntax, but 'client' will be null