The Most Difficult Concepts in Core Java?

Greetings. I was currious what subjects you all think are the most difficult subjects in core Java. This does not include theextension interfaces such as the J2EE stuff. Just the core. The issues can either be something you dont understand or something you mastered with dificulty.

My opinion is that anybody who's had a data structures class won't have trouble with the Collections API. There are really two branches to know: Collection and Map. Everything underneath is just knowing when choose between a LinkedList, Vector, or Stack.
I'd agree that threading trips people more often.
I'd also vote for RMI, because getting it right can be tricky. It's the basis for so much that's advanced: EJBs, Jini, etc.
JMHO. I'm not looking to start any flame wars. - MOD

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The most difficult part in AP Payment

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Could you please share what is the most difficult part for AP payment in your opinion? As I am studying about it and I have no idea where to start.
Please let's share your experience.

Dear @yingsras,
Their is nothing that is difficult:)
It appears that you are starting off to learn Oracle Payments. You can review the user guide and implementation guide and start off from the Payment types, methods etc..
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Prictical Guidelines for core java

Hi Friends,
I want a book like "explorering in c" for Core Java.
I am facing some problem, while executing the small tricky program of core Java.
I want a book which is related with practical oriented.
Means small junk of code and I have to calculate the out put or compilation error or run time error or which type of exception it will give.
Is there any book like this?
Or please give me this link
Please suggest me the book name or website name..........

"Thinking in Java" is quite good; the 3rd edition is a free e-book; downloadable from the author's web site http://www.mindviewinc.com/

The future of java and what is the most necessary skill to learn

hi, friends,
This is a serious question, so please answer seriously.
1. The future of java
Are there any future for java? What I mean are: are there any jobs for java developer in the future? are there any chances for new java company to survive?
2. What is the most needed skill in so many java technology?
There are so many sections in java technology. so what is the most needed one for one to find a job? what is the most promising section for one to build a company.
Thank your very much!

It's a lousy question really.
1) There are very few companies you'd call a 'java company'. There are companies that use java, but they also by and large use C++, DBMS systems, and a whole host of other technologies. If java died, they'd switch to whatever technology killed it. Any decent programmer is flexible enough to learn a new language in a matter of weeks. It's the ability to work with the theory behind the code rather than the knowledge of syntax that's important.
2) It depends entirely on what you're doing. Working with a company where databases are key? Then you need Oracle, or SQL. Working with web technology? Perl, JSP, PHP, stuff like that is what you want. Working in high performance application design? You need C++. Graphics? Take a look at OpenGL or Java3d.
The most promising section to build a company? If there was a straight answer to that 1000 companies would have sprung up already and filled the niche.
Basically, if you want a successful career in programming, don't become a java programmer, become a programmer full stop. If you think you'll be working with java when you retire in 40-odd years you're mistaken. You need to grasp the basic concepts of application and algorithm design, and be quick to learn new technologies and evaluate them against what exists already.
It can take 3 years to go from complete newbie to fluent in a single programming language. It can then take less than 3 days to become fluent in another.

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hi all, i have written an app which loops through a for loop within a for loop to send out tasks
i.e.
for( int i = 0; i < train.length; i++)
//load training file
for( int j = 0; j < test.length; j++ )
//load testing file
//train vs test
now that i have purchased aintel dual core e6600, what should i do to make the most out of it, system monitor currently tells me that one cpu is maxed out nad say 10% of the second cpu is in use so basically one cpu is idle, i would much rather be doing two of these tests at once, one by each cpu...i was thinking of making the tarin vs test part a thread and just keep calling start, but i am worried that as once the start has been made, another will be started and so on...and i dont want hundreds waiting to go as i ahve millions of these tests to do and i wont be able to hold it all in memory so i only want two running at a time, can anyone please help by offering some suggestions
thanks
Danny =)

i dont think you can control this from java.
Chances are that there is either a java version for that CPU + OS, in which case the JVM knowns what it is running on and how to make the system calls to manage the CPUs it uses. I really have 'doubt' that this is the case.
Most likely the JVM knows nothing about the dual core and the OS takes care of it, and even more likely the OS doesnt know anything about dual core and the hardware takes care of it.
i would think that its done mostly in hardware and a little bit on the OS level. I dont think applications should care about schedueling and let the OS/HW take care of that.

What is the diffrence between map and map.entry in core java

what is the diffrence between map and map.entry in core java . where it will be use ful. any one give one example plz.

A Map contains Map.Entry's
e.g.
        Map map = new LinkedHashMap(8);
        map.put(new Integer(1), "one");
        map.put(new Integer(2), "two");
        final Iterator iterator = map.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry entry = (Map.Entry) iterator.next();
            System.out.println("key=" + entry.getKey() + ", value=" + entry.getValue());
        }

Ive recently updated my mac to OS X 10.10 and now my CS5 illustrator and photoshop will not open... I uploaded the most recent Java and they still won't open. Please help

Ive recently updated my mac to OS X 10.10 and now my CS5 illustrator and photoshop will not open... I uploaded the most recent Java and they still won't open. Please help

Mac,
Nothing shows up here?
https://www.adobe.com/account/my-products-services.html#
With CS5 you must have registered, hopefully under your present Adobe ID.
I am afraid the chat and phone support are off until the beginning of January.
Serial number and activation support (non-CC, chat open between 5AM and 7PM PST/PDT on workdays)
http://helpx.adobe.com/x-productkb/global/service1.html
Adobe ID and registration support (non-CC, chat open between 5AM and 7PM PST/PDT on workdays)
http://helpx.adobe.com/x-productkb/global/service-c1.html
http://helpx.adobe.com/adobe-connect/adobe-connect-phone-numbers.html

Why do I keep getting an error "The new Java Plug-In requires a recent version of the Firefox Browser (Firefox 3 or later) I am using 3.6.13 and have the most up to date verison of Java according to their test site.

I was getting this error on an older windows xp pro machine and now it is appearing on a brand new windows 7 professional machine. I have confirmed the most up to date version of Java.

Start Firefox in [[Safe Mode]] to check if one of the add-ons is causing the problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).
* Don't make any changes on the Safe mode start window.
* [[Troubleshooting extensions and themes]]
You can also try "Reset all user preferences to Firefox defaults" on the [[Safe mode]] start window.

Compiling the java file related to Servlet and Core java files in heirarchy

I am working in Jakarta-Tomcat 4.0.4 with j2sdk1.4.1_01 and i have put all servlet files in package "com.java.servlet"
and other core java files in package "com.java.action" . Also I am imorting java files in package
"com.java.action" to the package "com.java.servlet".
But when I am compiling the servlet files in package "com.java.servlet"
then the servlet files are not compiling because it cannot able to import
java files in package "com.java.action" . I have tried all the options.
If anybody has solution then please respond immediately.

I agree with the previous poster, this sounds like a generic compiling problem. FYI: I do not think that packages that start with "com.java." are special or reserved in any way.
You are making a servlet, not a JSP, right? Since this is merely about compiling, you might want to re-post to "Java Programming".

Should I disable older Java Consoles in favor of the most current?

I've got many instances of the Java Console listed. Should I go ahead and disable all but the most current?

You can uninstall and remove Java Console extensions, you do not need them to run Java applets.
See:
* http://kb.mozillazine.org/Java#Multiple_Java_Console_extensions

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Hi all,
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My question is how do I get a Stored Procedure to wait (for a certain time period, once it times out the Stored Procedure can carry on but in an error state.) - (Like the "wait" in Java)
And then another Stored Procedure to break this waiting state. (Like the "notify" Java).
When the second stored procedure breaks the waiting state, the first stored procedure can carry on with it thread of execution.
I have tried to use DBMS_Locks, but uncovered a few hiccups.
Is there anything else I can try? ...
Regards,
Hilton

Hi John,
Thanks for the input, I have tried the using DBMS_Pipe and seems to have solved by problem.
Will look into the DBMS_Alert as well.
Thanks Again
Hilton

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no, you don't want to do that.
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And then there's the little matter of figuring out the external API to use that program in the way you intent to (if it has one).

What is the most effective way to get my imac 2 ghz intel core duo 2 10.4.11 to be able to run 10.5 and sync with my iphone 4s?

What is the most effective way to get my imac 2 ghz intel core duo 2 10.4.11 to be able to run 10.5 and sync with my iphone 4s?

As your Mac should run Snow Leopard provided it has at least 1GB memory, that would be a good deal easier and very much cheaper than trying to find a 10.5 install disc.
Snow Leopard costs $30 approx from the online Apple store (£26 if you're in UK)
You'll need to update Tiger to 10.4.11 with the combo installer first (unless you're just erasing the disc and starting fresh) You can then update SL from 10.6.3 to 10.6.8 with its combo installer.
For comparison, 10.5 Leopard is currently running about $130 from Apple (if still available) and more on Amazon etc.
This info for Leopard courtesy of TexasMacMan;
Mac OS X 10.5 Leopard installation system requirements
http://support.apple.com/kb/TA24950
Leopard is no longer available at the Apple Store but may be available by calling Apple Phone Sales @ 1-800-MY-APPLE (1-800-692-7753).
If you can't obtain a retail install DVD from Apple, look on eBay or Google the installer part numbers to possibly find at an on-line store. Here's what to look for:
MB427Z/A Leopard 10.5.1 install DVD
MB576Z/A Leopard 10.5.4 install DVD
MB021Z/A Leopard 10.5.6 install DVD (single user)
MB022Z/A Leopard 10.5.6 install DVD (5-user family pack)
Installing Mac OS X 10.5 Leopard
http://support.apple.com/kb/HT1544
Mac OS X 10.5 Leopard Installation and Setup Guide
http://manuals.info.apple.com/en/leopard_install-setup.pdf
After you install the base 10.5, download & install the 10.5.8 combo update at http://support.apple.com/downloads/Mac_OS_X_10_5_8_Combo_Update

After updating to OS 10.8.3 java does not function. I've validated the most current version of Java is installed. Has anyone else had this issue?

After updating to OS 10.8.3 java does not function. I've validated that the most current version of Java is installed and active in Safari. Has anyone else had this problem?

Yes indeed. See this thread - I have found a fix, but I am hoping once the engineers see this (Bug filed) that someone has an easier method, or a patch.
Something went wrong with the update in certain instances and it kills the Java plugin. Give this a shot - it takes a bit of time, but worthwhile.
https://discussions.apple.com/message/21528056#21528056
medward wrote:
After updating to OS 10.8.3 java does not function. I've validated that the most current version of Java is installed and active in Safari. Has anyone else had this problem?

I keep getting a new tab asking me to update Firefox & JAVA but I already have the most current versions. I also am getting ads on the homepage

After updating the most current Firefox I now get Ads on the home page that I can't get rid of even with the "X" box on the window. I have to shut down Firefox and start over to get anywhere. I didn't have this problem before the update.
I also had a change to the new tab/page feature. I used to click for a new tab and a series of boxes would show where I've been so I can perhaps select one. That feature has changed and I now get a tab/page that says it is owned by AVG. Where is my old page

If it opens in a new tab it is likely fake.
Can you post a link of it, you may also want to check for malware.
You can try these free programs to scan for malware, which work with your existing antivirus software:
* [http://www.microsoft.com/security/scanner/default.aspx Microsoft Safety Scanner]
* [http://www.malwarebytes.org/products/malwarebytes_free/ MalwareBytes' Anti-Malware]
* [http://support.kaspersky.com/faq/?qid=208283363 TDSSKiller - AntiRootkit Utility]
* [http://www.surfright.nl/en/hitmanpro/ Hitman Pro]
* [http://www.eset.com/us/online-scanner/ ESET Online Scanner]
[http://windows.microsoft.com/MSE Microsoft Security Essentials] is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.
Further information can be found in the [[Troubleshoot Firefox issues caused by malware]] article.
Did this fix your problems? Please report back to us!

The Most Difficult Concepts in Core Java?

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