330 Java Tips.pdf - FTP Server

General Java Questions II
I need a little help here...I have been teaching that constructors are not methods. This
is for several reasons, but mainly because JLS says "constructors are not members"
and members are "classes, interfaces, fields, and methods."
So, now the rest of the staff is ganging up on me and making life a little nasty. They
quote Deitel and Deitel, and Core Java (which references "constructor methods") and
who knows how many other books.
The one we are teaching in is loaded with so many errors that even though it calls
constructors methods NOBODY will quote it as an authority.
How can so many people call constructors methods if they aren't.
Okay. Are they or aren't they? I holding to the definition that they are not unless it is
so common to call them that, that I will have to change.
Comments?
Answer: If you go by the JLS (Java Language Specification) and the Java API (and
you should) , then no, constructors are not methods. Consider that
Class.getMethods() returns an array of Method instances and
Class.getConstructors() returns an array of Constructor instances, and Constructor
and Method or not interchangeable (one is not derived from the other), but both
implement the Member interface. Seems to me that Java is going out of its way to
differentiate them.
Besides, the mechanics of constructors are so different from the mechanics of
methods, there seems to be no value to considering one a member of the set of the
other.
Now, as far as teaching the language goes:
Methods:
+ return types
+ called by name
+ executed multiple times
Constructors:
+ super(...) or this(...) as first instructor (often implicit)
- everything else
I very much do not like trying to lump the two concepts together, especially in
introductory courses. Conceptually they are very, very different things.
A constructor is a unique element (even if there are several). It has the name of the
class, its declaration is different, and it doesn't have the same syntax as a method. It
plays a unique role. You can call a method from a constructor, but you cannot call a
constructor from a method.
I say constructors are distinct from methods, and for students, blurring the distinction
will lead to problems.
-by
Chuck McCorvey, Chris Wolfe, Paul Lutus
Q: Simple question: why constructor doesn't work in following example?
class Start {
public void Start() {
System.out.println("Konstruktor START");
}
}
file:///F|/350_t/350_tips/general_java-II.htm (2 of 13) [2002-02-27 21:18:24]