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In my application I need to make use of multiple threads to make it work faster but I have been facing a situation where it says that unable to create native threads.
I have read that it is the RAM which decides the number of the threads a program can have which depends on the number of threads*stack size for each thread.
How do we know the stack size for a thread in Java? Can I decide stack size for thread on my own?
The number of native threads you can create depends on the OS. It's rather the OS that stops you from going to such a huge number, not the memory size.
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I have a thread dump. Now, I want to know how many threads are running, what is their run time, what is its current state.
I don't want to use third party tools. I need a java code which takes dump file as input and shows the o/p.The main purpose is to find how long the threads were waiting.I want to find the threads with longest wait time!!
Use jvisualvm.It comes with your JDK.
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Recently i was asked in an interview , how to read huge file (single file of 1TB) in java.I said by using Threading , we will create two File objects and one thread will read it from the beginning and other Thread will read from last. May be this is Stupid answer.And the Interviewer gave hint , by using Horizontal/Vertical Scaling , Clustering.
I have seen in Google there is no Example for Horizontal/Vertical Scaling , Clustering and reading files.can anyone help
This interview question is quite open; it tries to have you talk and think out loud. There will be many answers.
My personal interpretation:
Both scaling do not refer to classes or frameworks. They are concepts in architectures. Start with wikipedia if you are not clear on that.
Vertical scaling: here they probably want you to see how you can improve performance on a single host to get this huge file job done. This involves better disks, raid, multithreading of course. If any CPU/memory is heavily loaded, perhaps having more cpu and memory.
Horizontal scaling: this is usually about how to divide the problem across multiple jvm hosts to have the file processed concurrently, in a divide and conquer, scatter/gather pattern.
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Closed 8 years ago.
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How can I create JVM with fewer cpu and ram (resources) and give other access to it, while also ensuring that they cannot manipulate or view files or data of my system?
I want to create a web interface java compiler which everyone can use and would not like if other can manipulate my system.
If you use VirtualBox or another VM you can
choose the OS, it doesn't have to be the same.
choose all the files it can see
choose how much CPUs and memory it can use.
make it hard to break out of the virtual host and into the real host.
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I have 2 Jetty servers with the same problem,
The Jetty web app gets "freeze" every couple of hours.
(Freeze means that the console is not doing anything/unable to receive new requests)
During the "Freeze" I noticed that the JVM is using more swap than it usually does.
It seems like sort of a memory leak, even tough the system has enough memory.
I run the JVM with those run parameters:
-Xms8000m -Xmx280000m
Those are the RAM graphs (blank lines are what I called "freeze"):
See reference number 1 below
I also noticed the the garbage collector is not running very frequent.
Maybe it is related?
See reference number 2 below
I'd appreciate any input regarding a proper use of the garbage collector and any other ideas that would help resolve it
This is a spring/Hibernate based Application.
http://i.stack.imgur.com/VGOkM.jpg
http://i.stack.imgur.com/eI1mt.jpg
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I want to get the windows shutdown/logoff time by using java.I had tried
Runtime.getRuntime().addShutdownHook(new Message());
I ran this code,I didn't get shutdown time.
The JavaDoc is very clear of the method usage.
It says:
Registers a new virtual-machine shutdown hook.
That means the JVM, not the underlying OS.
You should consider C++ or reading the Windows event log for your requirement.