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From: Jim Janney <jjanney@shell.xmission.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: It doesn't like 'super' where ever I put it.
Date: Sun, 10 Jun 2012 10:26:44 -0600
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bilsch <bilsch01@gmail.com> writes:

> On 6/10/2012 7:02 AM, Jim Janney wrote:
>> bilsch<bilsch01@gmail.com>  writes:
>>> BUILD SUCCESSFUL (total time: 2 seconds)
>>
>> Try changing
>>
>>      public void CalcFrame1() {
>>
>> to
>>
>>      public CalcFrame1() {
>>
> OK.  Thanks.  Can you tell me why that makes a difference?

Constructors are fundamentally different from ordinary methods, so most
object-oriented languages use a different syntax for them.  In Java, a
constructor definition looks like a method, but without an explicit
return type and using a name that matches the class name.  In other
languages the syntax may be different -- for example, in Python the name
is always __init__ -- but the underlying idea is the same: constructors
are not ordinary methods and take a different syntax.

Why are constructors different?  Most classes have some code that you
want to run whenever a new object is created, and it would be tedious to
have to call it explicitly every time.  I used to mimic OOP in C and you
had to do things like

    struct Foo* foo = (struct Foo*) malloc(sizeof(struct Foo));
    foo->init();

Forcing all object creation to go through a constructor makes the code
simpler and more reliable.  And even when a class has a constructor that
appears to be empty, there's still some code that the compiler generates
automatically the make the new object a proper instance of its class.

-- 
Jim Janney