newSomething() instead of new Something

General Discussions
#1

I was looking at one of the nio demonstration examples and noticed this line:


// Charset and decoder for ISO-8859-15
private static Charset charset = Charset.forName("ISO-8859-15");
private static CharsetDecoder decoder = charset.newDecoder();

The first one is moderatly understandable since the method won’t create a new object. But the second line is it really necessary ?

What would be the problem if they simply use this:


private static CharsetDecoder decoder = new CharsetDecoder(charset);

Off topic: Don’t you wish sometimes you could use C++ syntax like this?


private static CharsetDecoder decoder(charset);
#2

The difference is that new CharsetDecoder(charset); must return a class of type CharsetDecoder, where as charset.newDecorder() can return a subclass.

Often this technique is used when the class in question is abstract and you are trying to hide the implementation details.

#3

It’s utilzing the Factory Method Design Pattern. Definetly one of the more useful deign patterns in my experience.

#4

I never actually do this myself (mostly out of laziness), but I still think all constructors should be forced private. Factory methods are cute.

#5

Strange how the “new” operator is looking so limited at the moment: it must allways return a new object (not an already existing link to some static object) and it must be a class of the type used in the operator (not a subclass of that type).

I wonder why using a “public new” at all to create a new object ?

#6

The usual naming is createSomething rather than newSomething is it not? getSomething seems to be used where there is a backing cache and you don’t expect it to return a unique instance.

#7

The most intuitive name for me would be simply make(args) or create(args). No need for the extra word. Java is already clutered with unnecessary long names.

#8

Ey, in your code you can do what you want, simply use create(), nobody restricts you there, if you think this is enough. But imagine you’ve got a factory-class that can create A-objects and B-objects. Then it would for sure be a good way to call the methods

A createA(); and
B createB();

About this long name issue: I rather have long names than
cnoiasw();

Arne

PS: cnoiasw means createNewObjectInAShortWay

#9

[quote=“arne,post:8,topic:25031”]
When you create an object from a factory isn’t it irrelevant what the real class of the object is ? You are going to work with it using the common base class interface anyway. If you need to make that distinction then perhaps you shouldn’t use a factory and create the object directly from its class.

When i said unnvecessarly long names i wasn’t refereing to abreviated names. I think a name should be as short as possible but wthout being cryptic.