Re: How to compare two classes instances - Java Discussion Boards

khurram_shahzad14-Jan-11 15:54

14-Jan-11 15:54

How i campare two objects, such that if i have class(given below) and i want to compare there two different instances then how ??

class MyNode {
MyNode left;
MyNode right;
}

Is there any possiblity to do that --->

public boolean MyFunction(MyNode toSearch, MyNode parentNode) {
MyNode currentNode = parentNode;
while(currentNode != toSearch) {
return true;
}
else {
currentNode = currentNode.left;
}
}
return false;

Re: How to compare two classes instances

Richard MacCutchan15-Jan-11 0:19

Richard MacCutchan

15-Jan-11 0:19

You should implement your own Equals() method in your class and use that to test for equality. Using the == and != operators will not give the result that you are looking for.

I must get a clever new signature for 2011.

Re: How to compare two classes instances

khurram_shahzad15-Jan-11 3:10

khurram_shahzad

15-Jan-11 3:10

but can you please give some guide line to do this ... such that one way in my mind is like this that i put an Interger property in class that are then use to identify different instanceof class .. such that 1 for 1st instance/node then 2 for 2nd and so on and then compare some thing like this NodeA.IntegerIdentifier == NodeB.IntegerIdentifier but i doesn't satisfy with this idea as it is not apply in real senario as because in programming we should try to make solution in some thing like general awy.
So is there any idea aur suggestion for me that how i achieve this equality problem/isue what ever Smile | :)

Re: How to compare two classes instances

Richard MacCutchan15-Jan-11 4:39

Richard MacCutchan

15-Jan-11 4:39

See here[^] for lots of information on object equality.

I must get a clever new signature for 2011.

Re: How to compare two classes instances

Cedric Moonen16-Jan-11 21:01

Cedric Moonen

16-Jan-11 21:01

I think the OP wanted to search for a specific class instance in a linked list (at least, that's what I guessed from his code snippet). Thus, his code using the == operator was fine.

Cédric Moonen
Software developer

Charting control [v3.0]
OpenGL game tutorial in C++

Re: How to compare two classes instances

Richard MacCutchan17-Jan-11 0:24

Richard MacCutchan

17-Jan-11 0:24

you are right Cédric, I did not spend enough time reading the question.

I must get a clever new signature for 2011.

Re: How to compare two classes instances

khurram_shahzad17-Jan-11 3:45

khurram_shahzad

17-Jan-11 3:45

Thanks A LLLot .... Thanks for your great help ....

Re: How to compare two classes instances

Cedric Moonen16-Jan-11 20:59

Cedric Moonen

16-Jan-11 20:59

khurram_shahzad wrote:
and i want to compare there two different instances then how ??

Your question is not really clear.

There's a difference between having the same instance and having two different instances which are the same. In the first case, you want to verify if you are talking about the same instance. That's what you do in the code sample you posted: you check wether currentNode is the same object as toSearch.
In the second case, you want to verify that two instances contain the same thing but they are most of the time two different objects.

In your case, from what I saw in your code sample, you want to verify whether you are talking about the same object. Thus, it is fine to write it the way you did and it will work fine (in fact, when you use the == operator with objects, it will compare if the adresses of the two objects are the same, thus return true if the two pointers point to the same class instance).

Cédric Moonen
Software developer

Charting control [v3.0]
OpenGL game tutorial in C++

Re: How to compare two classes instances

khurram_shahzad17-Jan-11 3:47

khurram_shahzad

17-Jan-11 3:47

Yes here im comparing to diffrent instace of same class .....
Thanks A LLLot .... Thanks for your great help .... Big Grin | :-D

which simulator/editor is good for JAVA

aesthetic.crazy13-Jan-11 11:11

aesthetic.crazy

13-Jan-11 11:11

Hi,
m a beginner for java, n i wanna know which simulator/editor is good for doin java programming plz.

Re: which simulator/editor is good for JAVA

RaviRanjanKr13-Jan-11 21:16

RaviRanjanKr

13-Jan-11 21:16

I do my Java programming with netbeans and Eclipse and till now these two editors are best editors for me.
[Specially Eclipse]

Re: which simulator/editor is good for JAVA

Richard MacCutchan13-Jan-11 22:15

Richard MacCutchan

13-Jan-11 22:15

Eclipse[^] is a very easy to use IDE for creating and testing Java programs, assuming you are reasonably familiar with the language. If you want a "drag & drop" program builder, then NetBeans[^] may be a better choice. In either case you should spend some time going through the Java Tutorials[^].

I must get a clever new signature for 2011.

Re: which simulator/editor is good for JAVA

TorstenH.14-Jan-11 0:03

TorstenH.

14-Jan-11 0:03

Eclipse. There is a wide spread support on this one.

Try to write as much as you can yourself - click&drop are not really helpful as you do not see the code behind the action.

I also recommend buying an old fashion book, it's much easier to read something in a book while programming than to switch the screen multiple times.

regards,
Torsten

I never finish anyth...

Re: which simulator/editor is good for JAVA

Richard MacCutchan14-Jan-11 0:28

Richard MacCutchan

14-Jan-11 0:28

TorstenH. wrote:
than to switch the screen multiple times.

Or get a second monitor. Wink | ;)

I must get a clever new signature for 2011.

Re: which simulator/editor is good for JAVA

aesthetic.crazy14-Jan-11 12:59

aesthetic.crazy

14-Jan-11 12:59

i want to study a code, a difficult n lengthy code, n was wondering if there is any option in any of these through which i can run the code step by step (simulator will run each step of the code n stop n then run the next one, like breakpoints) to get a better understanding of my program/code flow? which one is suitable n what is the name of such option?

Re: which simulator/editor is good for JAVA

aesthetic.crazy14-Jan-11 13:00

aesthetic.crazy

14-Jan-11 13:00

is there any software through which i can understand the flow of any code? or can have any diagrammatic view?

Re: which simulator/editor is good for JAVA

Richard MacCutchan15-Jan-11 0:07

Richard MacCutchan

15-Jan-11 0:07

aesthetic.crazy wrote:
n lengthy code, n was

I'm not sure what these 'n' characters mean, but please spell words in full so people can properly understand your questions. Remember that English is not everyone's first language.

As to your question you just need to use the built in debugger with Eclipse or NetBeans and single step through the code to see what is going on.

I must get a clever new signature for 2011.

Re: which simulator/editor is good for JAVA

aesthetic.crazy15-Jan-11 12:09

aesthetic.crazy

15-Jan-11 12:09

I have this version of eclipse but i didnt find Debug single step option anywhere, kindly guide me.

Eclipse IDE for Java Developers

Version: Helios Service Release 1
Build id: 20100917-0705

Re: which simulator/editor is good for JAVA

Richard MacCutchan15-Jan-11 21:38

Richard MacCutchan

15-Jan-11 21:38

Go to your source file and double click a line of code to set a breakpoint, then using the menu find the Debug -> Run command and it will launch Java in debug mode. Or you could use the built in help.

I must get a clever new signature for 2011.

startNetworkServer

pancakeleh11-Jan-11 21:11

pancakeleh

11-Jan-11 21:11

i am using netbeans and i want to host a local dtaabase so i used the java db. However when i launch the startNetworkServer, i get the follow error.

http://img830.imageshack.us/img830/9448/whym.png[^]

anyone? who knows the solution?

Re: startNetworkServer

Richard MacCutchan11-Jan-11 21:20

Richard MacCutchan

11-Jan-11 21:20

The message seems fairly clear to me: either the file does not exist or you do not have access rights to that directory.

I must get a clever new signature for 2011.

Re: startNetworkServer

TorstenH.11-Jan-11 21:39

TorstenH.

11-Jan-11 21:39

Yes, Richard says it: It's a FileNotFoundException.

Looks like a Win7 machine. Files in the "Programm Files"-folder are not allowed to be changed by other files. Set permission on the derby-stuff.

regards
Torsten

I never finish anyth...

Re: startNetworkServer [modified]

pancakeleh11-Jan-11 21:49

pancakeleh

11-Jan-11 21:49

yup i am using a win 7. How shld i go abt solving it?
Frown | :(

http://img600.imageshack.us/img600/8999/capture1ml.png[^]

Right now when i run the startNetworkServer, there isnt any access deny but when i try to connect to the database, it will have the error shown above.

I have a local database deployed on my local pc. is there any way i can connect my laptop to the local database from my local pc so that i need not create one for my laptop but still able to use the database?

modified on Wednesday, January 12, 2011 4:01 AM

Re: startNetworkServer

TorstenH.12-Jan-11 0:17

TorstenH.

12-Jan-11 0:17

The server is not accepting your connection... why? is it the right address?
Confused | :confused:

regards
Torsten

I never finish anyth...

Re: startNetworkServer

pancakeleh12-Jan-11 19:36

pancakeleh

12-Jan-11 19:36

i manage to connect to my desktop's local connection already Smile | :)

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