Groups > comp.lang.java.programmer > #32604 > unrolled thread

can you give me some hints on the Oracle Java SE related certificates?

Started by	John <xsli2@yahoo.com>
First post	2015-09-18 07:55 -0700
Last post	2015-09-22 11:17 -0400
Articles	18 on this page of 38 — 7 participants

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#32627

From	Jeff Higgins <jeff@invalid.invalid>
Date	2015-09-22 09:16 -0400
Message-ID	<mtrkba$o8e$2@dont-email.me>
In reply to	#32626

On 09/22/2015 09:14 AM, Jeff Higgins wrote:
> On 09/22/2015 08:47 AM, Jeff Higgins wrote:
> ... In turn, his students will tell John if his
>> lesson satisfies their requirements and if they indicate need for
>> adjustments he will make those adjustments and present a "better" text
>> to his next batch of students.
>
> Just for kicks, google:
> java+multiple+inheritance, and
> java+appropriate+certificate.
>
Er, java+appropriate+certification

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#32628

From	Jeff Higgins <jeff@invalid.invalid>
Date	2015-09-22 09:32 -0400
Message-ID	<mtrl9c$sc0$1@dont-email.me>
In reply to	#32626

On 09/22/2015 09:14 AM, Jeff Higgins wrote:
> On 09/22/2015 08:47 AM, Jeff Higgins wrote:
> ... In turn, his students will tell John if his
>> lesson satisfies their requirements and if they indicate need for
>> adjustments he will make those adjustments and present a "better" text
>> to his next batch of students.
>
> Just for kicks, google:
> java+multiple+inheritance

The first hit in my browser:
<https://docs.oracle.com/javase/tutorial/java/IandI/multipleinheritance.html>

The third hit in my browser:
<http://javapapers.com/core-java/why-multiple-inheritance-is-not-supported-in-java/>

Then I read the Venner interview with Gosling:
<http://www.artima.com/intv/gosling13.html>

What is a poor student to think?

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#32633

From	Jeff Higgins <jeff@invalid.invalid>
Date	2015-09-22 09:54 -0400
Message-ID	<mtrmhj$1ja$1@dont-email.me>
In reply to	#32628

On 09/22/2015 09:32 AM, Jeff Higgins wrote:
>
> What is a poor student to think?

John seems to be leaning toward the "No multiple inheritance
in Java" camp. I feel more comfortable with the broader
interpretation.

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#32629

From	e.d.programmer@gmail.com
Date	2015-09-22 06:34 -0700
Message-ID	<26185e54-0f8f-432c-949d-baed732b728e@googlegroups.com>
In reply to	#32625

On Tuesday, September 22, 2015 at 8:49:41 AM UTC-4, Jeff Higgins wrote:
> I suspect that teaching « A » programming language is very hard to get
> right. I'll point to the super abundance of Java teaching material that
> is available, and the variability of the quality of that material as
> grounds for my suspicion. One reason for the difficulty might be that
> a programming language doesn't live in a vacuum. Fitting your lessons
> to a body of students will require evaluating prior knowledge and future
> needs.
> 
> This thread descending from the original article posted by John has
> morphed into a discussion of "Multiple inheritance in Java". If one
> were to decide to teach a lesson on this topic he would do his
> evaluations, and depending upon the outcome he might decide that the
> statements you propose above perfectly fit the bill.
> 
> The links to the Oracle Java Tutorials to which I pointed above, and
> to which John objected that I hadn't put into my own words, take another
> tack. Scott, in his "Programming Language Pragmatics" takes yet another.
> John, hopefully having done his evaluations, will produce a lesson and
> present it to his students. In turn, his students will tell John if his
> lesson satisfies their requirements and if they indicate need for
> adjustments he will make those adjustments and present a "better" text
> to his next batch of students.

Indeed teaching Java is all about explaining to students in words they understand.  If they already were able to understand without assistance, anyone with internet access could learn by browsing https://docs.oracle.com/javase/tutorial/index.html

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#32630

From	Jeff Higgins <jeff@invalid.invalid>
Date	2015-09-22 09:36 -0400
Message-ID	<mtrlfk$t0e$1@dont-email.me>
In reply to	#32629

On 09/22/2015 09:34 AM, e.d.programmer@gmail.com wrote:

> Indeed teaching Java is all about explaining to students in words they understand.  If they already were able to understand without assistance, anyone with internet access could learn by browsing https://docs.oracle.com/javase/tutorial/index.html
>
Maybe they need the credits.

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#32632

From	Jeff Higgins <jeff@invalid.invalid>
Date	2015-09-22 09:50 -0400
Message-ID	<mtrmbe$vr4$1@dont-email.me>
In reply to	#32629

On 09/22/2015 09:34 AM, e.d.programmer@gmail.com wrote:
anyone with internet access could learn by browsing
<https://docs.oracle.com/javase/tutorial/index.html>

A generous instructor might point out that the Java Tutorials
are available a a single large download in several forms and
also as a print book.

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#32635

From	Jeff Higgins <jeff@invalid.invalid>
Date	2015-09-22 10:56 -0400
Message-ID	<mtrq5o$g3t$1@dont-email.me>
In reply to	#32632

On 09/22/2015 09:50 AM, Jeff Higgins wrote:
> On 09/22/2015 09:34 AM, e.d.programmer@gmail.com wrote:
> anyone with internet access could learn by browsing
> <https://docs.oracle.com/javase/tutorial/index.html>
>
> A generous instructor might point out that the Java Tutorials
> are available a a single large download in several forms and
> also as a print book.
>
>
In fact a very generous instructor might offer something like a
LiveCD with an essentially complete learning environment pre-
installed.

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#32624

From	e.d.programmer@gmail.com
Date	2015-09-22 05:26 -0700
Message-ID	<c8f4c39f-3b53-4925-abf1-90062537e19b@googlegroups.com>
In reply to	#32620

On Monday, September 21, 2015 at 4:57:52 PM UTC-4, John wrote:
---
Inheritance is not the same as Implementation.  Classes make objects.  Everything is an object.  Use vehicles for example.  A vehicle cannot be (extend) both car and truck.  They have different mutually exclusive properties.

Car and Truck extend Vehicle.  Honda Civic extends Car.  Ford F150 extends Truck.  Honda Civic and Ford F150 automatically get all the properties and methods of Vehicle (hasEngine, hasWheels).  This is Inheritance.

Interface connects potentially unrelated objects.  Rather than duplicate the logic at different inheritance branches for Diesel Truck and Diesel Car, and Gas Truck and Gas Car, we make Diesel Vehicle and Gas Vehicle interfaces to be able to fuel these different kinds of cars and trucks.  Honda Civic and Ford F150 may implement either of these.

If you can find real world examples it may be easier for your students to remember than whether they were implementing ClassA or extending ClassB, which might be easier if you name the interface InfcA.  An interface is not a Class, or a "Base".  It's just a shared set of properties and/or methods.

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#32631

From	Jerry Stuckle <jstucklex@attglobal.net>
Date	2015-09-22 09:50 -0400
Message-ID	<mtrm76$c7$1@dont-email.me>
In reply to	#32624

On 9/22/2015 8:26 AM, e.d.programmer@gmail.com wrote:
> On Monday, September 21, 2015 at 4:57:52 PM UTC-4, John wrote:
> ---
> Inheritance is not the same as Implementation.  Classes make objects.  Everything is an object.  Use vehicles for example.  A vehicle cannot be (extend) both car and truck.  They have different mutually exclusive properties.
> 
> Car and Truck extend Vehicle.  Honda Civic extends Car.  Ford F150 extends Truck.  Honda Civic and Ford F150 automatically get all the properties and methods of Vehicle (hasEngine, hasWheels).  This is Inheritance.
> 
> Interface connects potentially unrelated objects.  Rather than duplicate the logic at different inheritance branches for Diesel Truck and Diesel Car, and Gas Truck and Gas Car, we make Diesel Vehicle and Gas Vehicle interfaces to be able to fuel these different kinds of cars and trucks.  Honda Civic and Ford F150 may implement either of these.
> 
> If you can find real world examples it may be easier for your students to remember than whether they were implementing ClassA or extending ClassB, which might be easier if you name the interface InfcA.  An interface is not a Class, or a "Base".  It's just a shared set of properties and/or methods.
> 

No, a vehicle cannot be both a car and a truck.  However, a vehicle CAN
be both a car and a Honda.  It can also be both a truck and a Ford.  And
both Honda and Ford may derive from Manufacturer and contain information
specific to that manufacturer.

Additionally, Diesel and Gas could also be classes - there is an "is-a"
relationship between the car and the fuel.  Without multiple
inheritance, you have to derive gas_car, diesel_car, gas_truck,
diesel_truck from car and truck, respectively, or from gas_vehicle and
diesel_vehicle.  Either way you will have duplicate methods and
properties at some point (try it).

Multiple inheritance can be a very useful technique - one that I have
used occasionally in C++.  The biggest problem I've seen with it is
misuse.  But it's one I definitely miss in Java.

-- 
==================
Remove the "x" from my email address
Jerry Stuckle
jstucklex@attglobal.net
==================

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#32634

From	Jeff Higgins <jeff@invalid.invalid>
Date	2015-09-22 10:09 -0400
Message-ID	<mtrneq$5he$1@dont-email.me>
In reply to	#32631

On 09/22/2015 09:50 AM, Jerry Stuckle wrote:

> No, a vehicle cannot be both a car and a truck.
<http://www.pickuptrucks.com/html/stories/history/utes/page1.html>
The 1960 Ranchero pictured appeals to me because I started out in
a 1962 Fairlane.

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#32640

From	Sebastian <news@seyweiler.dyndns.org>
Date	2015-09-23 15:25 +0200
Message-ID	<mtu980$75h$1@news.albasani.net>
In reply to	#32631

Am 22.09.2015 15:50, schrieb Jerry Stuckle:
[snip]
> Multiple inheritance can be a very useful technique - one that I have
> used occasionally in C++.  The biggest problem I've seen with it is
> misuse.  But it's one I definitely miss in Java.
>
I think so far it has not been mentioned in this thread that Java does 
have indeed multiple inheritance of behavior with default methods in 
interfaces, since Java 8.

-- Sebastian

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#32641

From	Eric Sosman <esosman@comcast-dot-net.invalid>
Date	2015-09-23 09:43 -0400
Message-ID	<mtua5t$70n$1@dont-email.me>
In reply to	#32640

On 9/23/2015 9:25 AM, Sebastian wrote:
> Am 22.09.2015 15:50, schrieb Jerry Stuckle:
> [snip]
>> Multiple inheritance can be a very useful technique - one that I have
>> used occasionally in C++.  The biggest problem I've seen with it is
>> misuse.  But it's one I definitely miss in Java.
>>
> I think so far it has not been mentioned in this thread that Java does
> have indeed multiple inheritance of behavior with default methods in
> interfaces, since Java 8.

     Only to the same extent as in earlier Java versions, though.
All that Java 8 added was default implementations of the specified
methods, not the (potential) multiple inheritance.

     That is, even in Java 1 you could get into trouble:

	interface Muggle {
	    void spell(String word);
	}

	interface Wizard {
	    void spell(String charm);
	}

	class Rowling implements Muggle, Wizard {
	    // Which kind of spell() should I implement?
	}

... or even worse:

	interface Machine {
	    /** Operate the machine. */
	    void operate();
	}

	interface Surgeon {
	    /** Return true iff the patient survives. */
	    boolean operate();
	}

	class Autodoc implements Machine, Surgeon {
	    // This class cannot be written
	}

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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#32642

From	Jeff Higgins <jeff@invalid.invalid>
Date	2015-09-23 10:54 -0400
Message-ID	<mtuedv$odl$1@dont-email.me>
In reply to	#32641

On 09/23/2015 09:43 AM, Eric Sosman wrote:
> On 9/23/2015 9:25 AM, Sebastian wrote:
>> Am 22.09.2015 15:50, schrieb Jerry Stuckle:
>> [snip]
>>> Multiple inheritance can be a very useful technique - one that I have
>>> used occasionally in C++.  The biggest problem I've seen with it is
>>> misuse.  But it's one I definitely miss in Java.
>>>
>> I think so far it has not been mentioned in this thread that Java does
>> have indeed multiple inheritance of behavior with default methods in
>> interfaces, since Java 8.
>
>      Only to the same extent as in earlier Java versions, though.
> All that Java 8 added was default implementations of the specified
> methods, not the (potential) multiple inheritance.
>
>      That is, even in Java 1 you could get into trouble:
>
>      interface Muggle {
>          void spell(String word);
>      }
>
>      interface Wizard {
>          void spell(String charm);
>      }
>
>      class Rowling implements Muggle, Wizard {
>          // Which kind of spell() should I implement?
>      }
>
> ... or even worse:
>
>      interface Machine {
>          /** Operate the machine. */
>          void operate();
>      }
>
>      interface Surgeon {
>          /** Return true iff the patient survives. */
>          boolean operate();
>      }
>
>      class Autodoc implements Machine, Surgeon {
>          // This class cannot be written
>      }
>
 From the JLS 8:

Example 8.1.5-3. Illegal Multiple Inheritance of an Interface
interface I<T> {}
class B implements I<Integer> {}
class C extends B implements I<String> {}
Class C causes a compile-time error because it attempts to be a subtype 
of both I<Integer>
and I<String>.

Bringing the overloaded term "Multiple Inheritance" into a beginning
Java programming course in a fashion such as "No multiple inheritance
in Java" and all of its variants is harmful. If you have to bring it in
at least do it as in the example provided by the Java tutorials. If a
particular student needs more information point him to it and carry on.

That is my opinion.

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#32647

From	Sebastian <news@seyweiler.dyndns.org>
Date	2015-09-24 15:30 +0200
Message-ID	<mu0tto$9f4$1@news.albasani.net>
In reply to	#32642

Am 23.09.2015 16:54, schrieb Jeff Higgins:
[snip]
> Bringing the overloaded term "Multiple Inheritance" into a beginning
> Java programming course in a fashion such as "No multiple inheritance
> in Java" and all of its variants is harmful. If you have to bring it in
> at least do it as in the example provided by the Java tutorials. If a
> particular student needs more information point him to it and carry on.
>
> That is my opinion.

I guess avoiding the term altogether will do no good, as every student 
will come across it sooner or later on Google. Better prepare them.

You can't really avoid the topic when teaching interfaces. The Java 
tutorial is quite clear:

"Multiple inheritance of implementation is the ability to inherit method 
definitions from multiple classes. [...]  Default methods introduce one 
form of multiple inheritance of implementation."

Quoted from
https://docs.oracle.com/javase/tutorial/java/IandI/multipleinheritance.html

-- Sebastian

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#32648

From	Jeff Higgins <jeff@invalid.invalid>
Date	2015-09-24 10:19 -0400
Message-ID	<mu10pp$l9a$1@dont-email.me>
In reply to	#32647

On 09/24/2015 09:30 AM, Sebastian wrote:
> Am 23.09.2015 16:54, schrieb Jeff Higgins:
> [snip]
>> Bringing the overloaded term "Multiple Inheritance" into a beginning
>> Java programming course in a fashion such as "No multiple inheritance
>> in Java" and all of its variants is harmful. If you have to bring it in
>> at least do it as in the example provided by the Java tutorials. If a
>> particular student needs more information point him to it and carry on.
>>
>> That is my opinion.
>
> I guess avoiding the term altogether will do no good, as every student
> will come across it sooner or later on Google. Better prepare them.
>
> You can't really avoid the topic when teaching interfaces. The Java
> tutorial is quite clear:
>
> "Multiple inheritance of implementation is the ability to inherit method
> definitions from multiple classes. [...]  Default methods introduce one
> form of multiple inheritance of implementation."
>
> Quoted from
> https://docs.oracle.com/javase/tutorial/java/IandI/multipleinheritance.html
>
Yes. You've pretty much managed to restate my position.

What I am advocating against are blanket unqualified statements such as 
the OP's challenge to me upthread --

"Can you explain to me why Java cannot have multiple inheritance? Please 
note, I am asking WHY. This is Java 101 question."

My reply to which also pointed to:
Multiple Inheritance of State, Implementation, and Type
https://docs.oracle.com/javase/tutorial/java/IandI/multipleinheritance.html

I then pointed to an interview with James Gosling explaining why
he chose to implement multiple inheritance as he did.

I then pointed to resources that explain the term 'multiple inheritance"
in a broader context for the student that wants more information.

My intent is not a complete ban of the term, rather a good definition.

If my ramblings here said or implied otherwise, thank you for the
opportunity to correct them here.

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#32649

From	Sebastian <news@seyweiler.dyndns.org>
Date	2015-09-24 17:12 +0200
Message-ID	<mu13s3$ki5$1@news.albasani.net>
In reply to	#32648

Am 24.09.2015 16:19, schrieb Jeff Higgins:
[snip]
>
> My intent is not a complete ban of the term, rather a good definition.
>
> If my ramblings here said or implied otherwise, thank you for the
> opportunity to correct them here.
>
Thanks for the clarification.

[Scare quotes throughout in the following.]

I suppose that a "good" definition is a definition that serves its 
purpose in a given context. It may be difficult to arrive at a "good" 
definition in the sense of "correct" or "universally accepted".

Consider that Java multiple inheritance through interface methods is 
"only" behavioral. No state can be inherited, because all fields in an 
interface are automatically static.

In comparison, Scala traits offer "true" multiple inheritance, including 
state, and also allow accessing the object that implements the trait 
(via the self reference).

Because of these differences, the use of default methods is more 
restricted. It would not be possible to implement class-dependent, 
stateful cross-cutting concerns like Loggable using them, for example.

Default methods were specifically designed for API extension, as shown 
in the tutorial examples. "True" multiple inheritance has never been a 
design goal.

So while Java may not have "true" multiple inheritance, it certainly has 
some form of multiple inheritance. Why not call it "behavioral multiple 
inheritance" ?

But then, who really cares? I myself, like you, am perfectly happy to 
simply assert that Java has multiple inheritance, plain and simple. All 
the rest is hairsplitting on a scale much too fine for any introductory 
Java course.

-- Sebastian

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#32651

From	Jeff Higgins <jeff@invalid.invalid>
Date	2015-09-24 12:05 -0400
Message-ID	<mu16vu$eve$1@dont-email.me>
In reply to	#32649

On 09/24/2015 11:12 AM, Sebastian wrote:
> ...
> But then, who really cares? I myself, like you, am perfectly happy to
> simply assert that Java has multiple inheritance, plain and simple. All
> ...

Much happier with that than Java has no multiple inheritance.
Perfectly happy to do without type linearization.

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#32636

From	Jeff Higgins <jeff@invalid.invalid>
Date	2015-09-22 11:17 -0400
Message-ID	<mtrrdk$l61$1@dont-email.me>
In reply to	#32624

On 09/22/2015 08:26 AM, e.d.programmer@gmail.com wrote:

> Inheritance is not the same as Implementation.
> Classes make objects.
 > Everything is an object.

The student in me wants to say,
"Fusk this, I wonder if it's too late to transfer to Pseudocode."

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csiph-web

can you give me some hints on the Oracle Java SE related certificates?

Contents

#32627

#32628

#32633

#32629

#32630

#32632

#32635

#32624

#32631

#32634

#32640

#32641

#32642

#32647

#32648

#32649

#32651

#32636