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Hi,all.Could anybody give me a detail describtion of the channel?(that is,something likes file channel,socket channel,etc.) or give me the relative link about it.Also,I want to know:
1.How the os implements the channel,does it need any hardwares to support?
2.What does it differ from the stream,in what situation,I should use it rather then the stream? What's its advantage?
Thanks to all.
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What 'channel' are you talking about?
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Please take file channel as an example to explain it,mainly focusing on thease questions:
1.How the os implements the file channel,does it need any hardwares to support? or it just a virtual concept?
2.Why I should use it instead of the file stream?
Thanks!
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The Channel[^] is a Java concept, implemented on top of the operating system. As the documentation states, this can be a hardware device, a file, a network socket, or a program component that is capable of performing one or more distinct I/O operations, for example reading or writing. The choice of when to use channels over streams is something you need to decide when designing your application, as it will depend on your requirements.
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I am developing a java application which after developing i want to sell off to some organisation, but i dont know how to package all my project files into one file for commercial because i dont think they need to be viewing my source code.
How can i pack them all in one setup file? 
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The simplest way is to put all your classes into a java archive via the jar command. You then need to send only the jar file(s) to your customers; see http://docs.oracle.com/javase/tutorial/deployment/index.html[^]. You could also try a Google search to see if there are any other setup applications applicable to Java apps.
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Do NOT include your source files. Only compiled files should be in the setup.
Make sure resources and config files are in and accessible.
Use Launch4j[^]. It's common used for creating a setup.
If you want to protect your code further on, use an obfuscation tool like ProGuard[^]. It will make the compiled code unreadable.
regards Torsten
I never finish anyth...
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Hi, You can find out some ready made tool to do this. i think you will find best tool for that.
modified 9-Sep-14 7:42am.
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In terms of thread safety:
How can it be determined an object escapes a method call, without using JVM escape analysis?
('Escaping' means that an object can be accessed after the method completes)
A couple of examples on how an object can escape a method call:
1) The method returns the object that was locally created:
public MyObject someMethod(){
MyObject localObject = new MyObject();
return localObject();
}
someMethod.changeSomething();
2) One of the methods called with the LocalObject as parameter, stores the LocalObject instance in a way that allows access to it from other threads.
MyMember member;
public void someMethod(){
LocalObject localObject = new LocalObject();
localObject.callMethod();
method2(localObject);
}
public void method2(LocalObject localObject){
localObject.setValue("value");
member = localObject;
}
Does anyone know any more practical examples on how an object can escape a method call?
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Neo10101 wrote:
No it can't. Not from that method.
Thread 1 calls that method. That method create a brand spanking new object and returns it to the caller.
Thread 2 calls that method. That method create a brand spanking new object and returns it to the caller.
Neither object is the same. The calling sequence of the threads 1 and 2 are irrelevant (again in the context of this method only) each will still get a new object which is untouchable by the other thread.
Neo10101 wrote: Does anyone know any more practical examples on how an object can escape a method call?
The method returns a data member of the class which is an object. So
public MyObject getMyObject() { return myObject; }
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Hi,
I just want to check that the given PDF file is 3D PDF or normal PDF file. Can some one know how can I do this in JAVA?
Regards,
Ravi
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You would need to check the PDF specification to see how to tell the difference. Although I am not sure there is such a thing as a "3D PDF file".
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I'm fairly new to programming especially ones that use database. I can make software that use database but only with .NET and using MySql with XAMPP. However I'm still trying to figure out how to do that in Java because I'm currently learning the language.
However I saw this application which is an application for saving solve times for rubik's cube speedsolves. The software is called Prisma Puzzle Timer. [Download]
The software generates a file with the .db extension on first run in the same directory of the .jar file. I assume this is the database.
My question is how can this be done? And what type of database is it? (the .db file extension)
Although the said software is open source, I don't have enough knowledge to understand the source to even find where the database creation is implemented (though I'm still trying to read through the source and I'm still in my learning phase in Java programming).
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The .db extension on the file tells us nothing, because it depends on the program that is generating it as to what format it takes. If you are interested in using databases from Java, and Java itself, then your time would be better spent studying the Java Tutorials[^].
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Ah, yes. I just got familiar with that file extension meaning nothing. I actually tried The Java Tutorials but I had a hard time understanding everything there. Perhaps I didn't had enough programming experience yet because I think they assume you've had C++ knowledge already. So I'm currently learning Java with other tutorials.
Anyway I'm familiar with MySql.
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extranghero wrote: I had a hard time understanding everything there. Perhaps I didn't had enough programming experience yet because I think they assume you've had C++ knowledge already.
No, you should be able to work through those tutorials without any previous programming experience. The introduction starts from the very basic concepts.
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I think what you mean is to have an embedded database in your application. Well in that case, you have a number of choices. I would suggest you look at [Hypersonic SQL^]. It is lightweight and quite mature.
Another option is to look at [Sqlite^]. I have not used it in a Java project before, but it is quite a nice and fast little database.
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Derby is another choice. Might be better for someone learning java.
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Alright I'll also read about this. Thanks. 
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Thanks! I will try to have a look at HyperSonic SQL. Hope this will work for me.
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A great thing about SQLite is the licence agreement which includes the text
"Anyone is free to copy, modify, publish, use, compile, sell, or distribute the original SQLite code, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means."
Nice to have that kind of freedom.
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Hello Dear Friend, I'm also having the same question. When you got to know the answer or code for this please do share it with me.
Gokul Gawande
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Well I think I'll settle with HyperSQL. I downloaded it. Comes with a nice documentation and that's what I'm reading now to learn it. I discovered the embedded database I saw on the example on my original post was something called H2. I think it's similar.
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