Different ways to create an object

Question

Hi All,
I am a new bie to java programming. I know the way to create an object for a class will be something like
A b = new A(); // A is the class name and b is the object name.
But i am not sure what the following code means, I know it is also creating an object but how and why in that manner.
CaptureSearchForm userBean = (CaptureSearchForm) form;
A b = (A) c;
If b is the object name, then what is c here?Can anyone please explain me in detail.
Also,
java.util.List pageList = new ArrayList();
Why should we give in the above manner? what does it mean?
Thanks in advance....,,,,

Answer 1

auto wrote:
But i am not sure what the following code means, I know it is also creating an object but how and why in that manner.
CaptureSearchForm userBean = (CaptureSearchForm) form;This does not create an object. It takes the value in the reference variable foram and copies it into the refernce variable userBean, so that userBean and form both point to the same object. The (CaptureSearchForm) is called a cast. It tells the compiler that even though form may not be declared to be of type CaptureSearchForm or a subclass, you the programmer know that the object it points to will be a CaptureSearchForm or a subclass, and to treat it as such. If at runtime this is not the case, you'll get a ClassCastException.
A b = (A) c;
If b is the object name, then what is c here?Can anyone please explain me in detail. b is not the object name. Objects do not have names. b and c are both variable names.
Also,
java.util.List pageList = new ArrayList();
Why should we give in the above manner? what does it mean?It's known as programming to the interface. On the LHS, you're saying that pageList must point to an object that implements List. You don't cae if it's an ArrayList or LinkedList or something else. It's a way to decouple your code from the specific implementations of the types it uses.