Solved

Is my definition of a generic method in Java ok?

Posted on 2011-09-14
13
301 Views
Last Modified: 2012-05-12
Here's my basic definition of a generic method. Is it acceptable?

Generic Method - a method in which type parameters appear within angled brackets, right before the return type. The code below is a generic method that uses an enhanced for loop to add array elements to a collection one by one. The third line of the code would not have compiled if the <T> at the beginning of the method signature was not there. That <T> made it possible for the array and the collection in the method parameter to be typed the same generic way, so that this method would be compatible with any object type.

static <T> void fromArrayToCollection(T[ ] a, Collection<T> c) {
     for (T o : a) {
        c.add(o); // adding an array element of type T
     }
}
0
Comment
Question by:shampouya
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 9
  • 4
13 Comments
 
LVL 47

Expert Comment

by:for_yan
ID: 36536407
Yes, this seems fine to me
0
 
LVL 47

Expert Comment

by:for_yan
ID: 36536412
if it compiles then it is fine
0
 
LVL 47

Expert Comment

by:for_yan
ID: 36536419
And it does compile fro me
0
SharePoint Admin?

Enable Your Employees To Focus On The Core With Intuitive Onscreen Guidance That is With You At The Moment of Need.

 
LVL 47

Expert Comment

by:for_yan
ID: 36536436
Although my IDE suggest to replcae it withh Collection.addAll method, but this does not matter; once it compiles it measn it is correct
0
 

Author Comment

by:shampouya
ID: 36536452
And the <T> after the word static is what turned this method into a generic method, right?
0
 
LVL 47

Expert Comment

by:for_yan
ID: 36536519
Yes, without that "T" in fromt of static compiler would not understdn what means T inside the mthod and in parameters
0
 
LVL 47

Expert Comment

by:for_yan
ID: 36536558
So this code compiles fine together with your method definition:

  
        Collection<String> cc = null;
        String [] cmcm = null;
        
            fromArrayToCollection(cmcm, cc);
        

Open in new window

0
 

Author Comment

by:shampouya
ID: 36536584
Oh I know it compiles, correctly, I took it from the Oracle website. I was just wondering if my english was correct when I defined a generic method. And I was wondering if the <T> before the return type is what can turn a regular method into a generic method.
0
 
LVL 47

Expert Comment

by:for_yan
ID: 36536589

Aslo this compiles:

        Collection<Object> cc = null;
        String [] cmcm = null;

            fromArrayToCollection(cmcm, cc);

Open in new window


but this does not:


Collection<String> cc = null;
        Object [] cmcm = null;

            fromArrayToCollection(cmcm, cc);

Open in new window


This is in compliance with your previous
statements about covariance of arrays and collections
0
 

Author Comment

by:shampouya
ID: 36536608
I'm confused and I'm not sure why you are telling me what compiles.That wasn't my question....
0
 
LVL 47

Expert Comment

by:for_yan
ID: 36536618
I just liked that your talks about covariance of arrays vs collections in previous question are nicely illustrated by this example
 
0
 
LVL 47

Accepted Solution

by:
for_yan earned 500 total points
ID: 36536657
And about "T" in front:

Compiler has to account for any entity when it parses the code - each entity is either a class or variable name or something
which compiler should yunderstand.
If you don't put "T" in front - it will parse "T" inside the metghod definition - and will not know what it is - when it
saw "T" in front of static it understandts that it is a generic method and will
be able to recignize what is "T" when it parses the contents of the method.

By the way you can use almost arbitrary striung instead of "T" - I replaced "T" by "MyT" in all places and it also works - it is just a tradition to use "T" for "type"
0
 

Author Closing Comment

by:shampouya
ID: 36536705
thanks
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

For beginner Java programmers or at least those new to the Eclipse IDE, the following tutorial will show some (four) ways in which you can import your Java projects to your Eclipse workbench. Introduction While learning Java can be done with…
By the end of 1980s, object oriented programming using languages like C++, Simula69 and ObjectPascal gained momentum. It looked like programmers finally found the perfect language. C++ successfully combined the object oriented principles of Simula w…
Viewers learn about the “for” loop and how it works in Java. By comparing it to the while loop learned before, viewers can make the transition easily. You will learn about the formatting of the for loop as we write a program that prints even numbers…
This tutorial explains how to use the VisualVM tool for the Java platform application. This video goes into detail on the Threads, Sampler, and Profiler tabs.

730 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question