locking

I am building an update system in which I need to be able to replace a referenced jar of a running application jar at runtime. However, I am running into file locking issues on Windows when trying to perform file utility functions on the jar such as 'setLastModified'. After some googling I found this snippet... What I found in my research is that the standard ClassLoader implementation never closes a jar file once it has been opened. It also only loads resources from the jar file as needed. So at any particular time, there may be Classes in the jar file that have not been loaded into memory.

I'm running a very computationally intensive scientific job that spits out results every now and then. The job is basically to just simulate the same thing a whole bunch of times, so it's divided among several computers, which use different OSes. I'd like to direct the output from all these instances to the same file, since all the computers can see the same filesystem via NFS/Samba. Here are the constraints: Must allow safe concurrent appends. Must block if some other instance on another computer is currently appending to the file. Performance does not count. I/O for each instance is only a

I'm currently trying to write a thread-safe logger class. I'm not very familiar with correct design and best practices in this area. Is there a flaw in my code? public class WriteStuff { private readonly StreamWriter m_Writer; private readonly object m_WriteLock = new object (); public WriteStuff(String path) { m_Writer = File.CreateText (path); m_Writer.WriteLine ("x"); m_Writer.Flush (); } public void ListenTo(Foo foo) { foo.SomeEvent += new EventHandler<SomeArgs> (Foo_Update); } private void Foo_Update(object sender, SomeArgs args) { lock (m_WriteLock) { m_Writer.WriteLine (args); m_Writer

The java meomry model mandates that synchronize blocks that synchronize on the same monitor enforce a before-after-realtion on the variables modified within those blocks. Example: // in thread A synchronized( lock ) { x = true; } // in thread B synchronized( lock ) { System.out.println( x ); } In this case it is garanteed that thread B will see x==true as long as thread A already passed that synchronized -block. Now I am in the process to rewrite lots of code to use the more flexible (and said to be faster) locks in java.util.concurrent , especially the ReentrantReadWriteLock . So the example

I have a website where users can purchase tickets, but ticket quantities are usually limited and go quickly. I'm trying to implement an escrow system such that a user can click that they want x number of tickets, at which point I will put them in an escrow state. That gives them several minutes to enter their credit card information and complete the purchase. I have three relevant tables: events, tickets, and escrow. A row in the events table describes the event itself, including the maximum number of tickets available. The tickets table holds the following: user_id : the user that purchased