Quick question about inheritance and exceptions

If I have two classes like this:
public class ClassA {
    public void myMethod() throws NumberFormatException {
      throw new NumberFormatException();
public class ClassB extends ClassA {
    public void myMethod() {
}Does myMethod() in classA override myMethod in classB?
And why?
Thank you,
V

I just want to add that since NumberFormatException is
a descendant of RuntimeException, you are not required
to declare that the method throws this exception. Some
people think it is a good idea to declare it anyway
for clarity. Personally, I don't think so.I agree.
I think Sun recommends that you don't declare unchecked exceptions in the method declaration, but do document them in the javadoc comments.

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A question about inheritance and overwriting

Hello,
My question is a bit complicated, so let's first explain the situation with a little pseudo code:
class A {...}
class B extends A{...}
class C extends B {...}
class D extends C {...}
class E extends B {...}
class F {
ArrayList objects; // contains only objects of classes A to E
void updateObjects() {
    for(int i = 0; i < objects.size(); i++)
      A object = (A) objects.get(i); // A as superclass
     update(A);
void update(A object) { ... }
void update(B object) { ... }
void update(D object) { ... }
}My question now:
For all objects in the objects list the update(? object) method is called. Is it now called with parameter class A each time because the object was casted to A before, or is Java looking for the best fitting routine depending on the objects real class?
Regards,
Kai

Why extends is evil
Improve your code by replacing concrete base classes with interfaces
Summary
Most good designers avoid implementation inheritance (the extends relationship) like the plague. As much as 80 percent of your code should be written entirely in terms of interfaces, not concrete base classes. The Gang of Four Design Patterns book, in fact, is largely about how to replace implementation inheritance with interface inheritance. This article describes why designers have such odd beliefs. (2,300 words; August 1, 2003)
By Allen Holub
http://www.javaworld.com/javaworld/jw-08-2003/jw-0801-toolbox.html
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http://www.javaworld.com/javaworld/jw-04-2001/jw-0413-polymorph_p.html
Summary
Java developers all too often associate the term polymorphism with an object's ability to magically execute correct method behavior at appropriate points in a program. That behavior is usually associated with overriding inherited class method implementations. However, a careful examination of polymorphism demystifies the magic and reveals that polymorphic behavior is best understood in terms of type, rather than as dependent on overriding implementation inheritance. That understanding allows developers to fully take advantage of polymorphism. (3,600 words) By Wm. Paul Rogers
multiple inheritance and interfaces
http://www.javaworld.com/javaqa/2002-07/02-qa-0719-multinheritance.html
http://java.sun.com/docs/books/tutorial/java/interpack/interfaceDef.html
http://www.artima.com/intv/abcs.html
http://www.artima.com/designtechniques/interfaces.html
http://www.javaworld.com/javaqa/2001-03/02-qa-0323-diamond_p.html
http://csis.pace.edu/~bergin/patterns/multipleinheritance.html
http://www.cs.rice.edu/~cork/teachjava/2002/notes/current/node48.html
http://www.cyberdyne-object-sys.com/oofaq2/DynInh.htm
http://www.gotw.ca/gotw/037.htm
http://www.javajunkies.org/index.pl?lastnode_id=2826&node_id=2842
http://saloon.javaranch.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic&f=1&t=001588
http://pbl.cc.gatech.edu/cs170/75
Downcasting and run-time
http://www.codeguru.com/java/tij/tij0083.shtml
type identification
Since you lose the specific type information via an upcast (moving up the inheritance hierarchy), it makes sense that to retrieve the type information ? that is, to move back down the inheritance hierarchy ? you use a downcast. However, you know an upcast is always safe; the base class cannot have a bigger interface than the derived class, therefore every message you send through the base class interface is guaranteed to be accepted. But with a downcast, you don?t really know that a shape (for example) is actually a circle. It could instead be a triangle or square or some other type.
To solve this problem there must be some way to guarantee that a downcast is correct, so you won?t accidentally cast to the wrong type and then send a message that the object can?t accept. This would be quite unsafe.
In some languages (like C++) you must perform a special operation in order to get a type-safe downcast, but in Java every cast is checked! So even though it looks like you?re just performing an ordinary parenthesized cast, at run time this cast is checked to ensure that it is in fact the type you think it is. If it isn?t, you get a ClassCastException. This act of checking types at run time is called run-time type identification (RTTI). The following example demonstrates the behavior of RTTI:
//: RTTI.java
// Downcasting & Run-Time Type
// Identification (RTTI)
import java.util.*;
class Useful {
public void f() {}
public void g() {}
class MoreUseful extends Useful {
public void f() {}
public void g() {}
public void u() {}
public void v() {}
public void w() {}
public class RTTI {
public static void main(String[] args) {
Useful[] x = {
new Useful(),
new MoreUseful()
x[0].f();
x[1].g();
// Compile-time: method not found in Useful:
//! x[1].u();
((MoreUseful)x[1]).u(); // Downcast/RTTI
((MoreUseful)x[0]).u(); // Exception thrown
} ///:~
As in the diagram, MoreUseful extends the interface of Useful. But since it?s inherited, it can also be upcast to a Useful. You can see this happening in the initialization of the array x in main( ). Since both objects in the array are of class Useful, you can send the f( ) and g( ) methods to both, and if you try to call u( ) (which exists only in MoreUseful) you?ll get a compile-time error message.
If you want to access the extended interface of a MoreUseful object, you can try to downcast. If it?s the correct type, it will be successful. Otherwise, you?ll get a ClassCastException. You don?t need to write any special code for this exception, since it indicates a programmer error that could happen anywhere in a program.
There?s more to RTTI than a simple cast. For example, there?s a way to see what type you?re dealing with before you try to downcast it. All of Chapter 11 is devoted to the study of different aspects of Java run-time type identification.
One common principle used to determine when inheritence is being applied correctly is the Liskov Substitution Principle (LSP). This states that an instance of a subclass should be substitutible for an instance of the base class in all circumstances. If not, then it is generally inappropriate to use inheritence - or at least not without properly re-distributing responsibilities across your classes.
Another common mistake with inheritence are definitions like Employee and Customer as subclasses of People (or whatever). In these cases, it is generally better to employ the Party-Roll pattern where a Person and an Organization or types of Party and a party can be associated with other entities via separate Role classes of which Employee and Customer are two examples.

Quick Question About Ringtones and iPhone

I've looked through the discussions and could not find my answer. If you know of a discussion already posted please refer me to that.
Question: After buying a song from iTunes is there a statute of limitations governing the song's ability to create a ringtone?
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Also, is there any program besides iTunes that can be used to create ringtones from any song?
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Message was edited by: Abe

No there is not a time limit that I know of. The bell has disappeared on mine too. Have you clicked Store>create ringtone?
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http://discussions.apple.com/thread.jspa?messageID=8613825&#8613825
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Probably a very simple question but I'm pretty new to PPro, so I'd appreciate your help...
I've got an uncompressed AVI video that I want to export to mp4 using several presets (that means several exports). What I intend to do is the following:
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I create a sequence and put my AVI file in there and then I just apply the preset.
Then on the same sequence, I clear the preset and apply a new one, and again without rendering, go to export and then to the encoding queue.
Does "apply the preset" mean selecting an encoding preset
before sending the Sequence to the Queue?
If I understand what you are trying to do...
It sounds like you want to do multiple, different format
exports from the same Premiere Sequence.
If so...
I would Queue the Sequence to Media Encoder once from Premiere,
then duplicate the entry in the Queue (Ctrl+D) and assign the
different encode types to the duplicates in Media Encoder,
(instead of Queueing the Sequence multiple times).
...will the export files each have the different preset applied even though it was not rendered?
A Sequence will be encoded using the assigned settings.
You can set multiple encodes in the Queue, each with different settings.
I'm not sure what you mean by "even though it was not rendered...".
Unless you have specified 'Use Preview Files' in your encoding,
it will make no difference if your Sequence is 'Timeline Preview'
rendered or not.

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oh sorry i misunderstood you
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i cant say for hp's
havent worked on any in a while
recent machines have been coupleof dell's , vaio & emachine
which dells do offer it at least the ones i tried , my laptop does(dell)
all home pc's are built by me which do offer to boot individual drives
what hp you getting it may tell in specs
are both discs sata? if so it might not offer this option with 2 drives of same interface
check your power supply alot of these preconfigured machines put cheap under reated power supplies in there
& will burn your motherboard i just replaced PS(250 watt) & mobo(845gvsr) in an emachines <cheap stuff<
i hope you researched the pc before buying ie : mobo, power supply are the biggest concerns
i find it much more benificial to build my own machine gives me peace at mind. the cost is sometimes more in $ but not always , your biggest expense is time researching hardware
if you live in usa the best places to start looking are bensbargains.net & pricewatch.com
i am not affiliated with either & niether sell the hardware they are just advertisers a place to buy
for costomized machines that i would trust is unitedmicro.com theyll asemble & test before shipping
i have gotten 2 machines so far from them with NO PROBLEMS with hardware (knock knock)
you may want to consider this in your next venture for pc

One very basic question about inheritance

One very basic question about inheritance.
Why we need inheritance?
the benefit of inheritance also achieve by creating instance of base class using it in other class instead of extending the base class.
Can any one please explain why we are using inheritance instead of creating object of base class????

SumitThokal wrote:
One very basic question about inheritance.
Why we need inheritance?
the benefit of inheritance also achieve by creating instance of base class using it in other class instead of extending the base class.
Can any one please explain why we are using inheritance instead of creating object of base class????What did you find out when you looked on Google?
One example of inheritance comes in the form of a vehicle. Each vehicle has similarities however they differ in their own retrospect. A car is not a bus, a bus is not a truck, and a truck is not a motorbike. If you can define the similarities between these vehicles then you have a class in which you can extend into either of the previous mentioned vehicles. Resulting in a reusable class, dramatically reduces the size of code, creates a single point of definition, increases maintainability, you name it.
In short there are thousands of benefits from using inheritance, listing the benefits could take a while. A quick Google search should give you a few hundred k if not million links to read.
Mel

Hi, I have quick question about use of USEBEAN tag in SP2. When I specify a scope of SESSION for the java bean, it does not keep the values that I set for variable in the bean persistent.Thanks,Sonny

Make sure that your bean is implementing the serializable interface and that
you are accessing the bean from the session with the same name.
Bryan
"Sandeep Suri" <[email protected]> wrote in message
news:[email protected]..
Hi, I have quick question about use of USEBEAN tag in SP2. When I
specify a scope of SESSION for the java bean, it does not keep the
values that I set for variable in the bean persistent.Thanks,Sonny
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Three questions about Java and Ftp

Hello, i've the following questions about Java and Ftp:
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FileWriter file = new FileWriter ("$HOME/.netrc");
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Kike

1- .netrc file is in $HOME directory but i can't
access to this directory from java code. The
following line producesan Exception (directory
doesn't exists)
FileWriter file = new FileWriter ("$HOME/.netrc");$HOME would have to be replaced by a shell, I don't
think you can use it as part of a legal path.
Instead, use System.getProperty("user.home");
Ok, thanks
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-rw- --- --- but when i create the .netrc file the
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how can i change this permissions? (In java code,i
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I need to use estrictly the .netrc with -rw- --- --- permissions
Yes, i can use Runtime.exec ("chmod ..."); but i don't like very much this solution because is a slow solution, am i right?
3- Are there any way to pass parameters to a.netrc
file? If i get to do this i needn't change the
permissions because i can't modify orcreate/destroy
this file.I don't think so. Why do you need the .netrc file in
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- use .netrc with parameters but i haven't found any help about it
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Kike

Quick question about inheritance and exceptions

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