What is the difference between a Collections.synchronizedMap() and a wrapper around a HashMap with all the methods synchronized. I dont see any difference becuase Collections.synchronizedMap() internally maintains the same lock for all methods. Basically, what is the difference between the following code snippets Class C { Obje...
Hi, I was going through some code snippets looking at the synchronization aspect. I believe locking happens on objects. In the case of java we only have references to objects. Java should use the reference to procure the object and lock it. What happens if the reference happens to be null? I feel this would break. If this were to work t...
This code will throw Concurrent Modification Exception if the list is modified in doSomething(). Is it possible to avoid it by enclosing the code in some synchronized block? List l = Collections.synchronizedList(new ArrayList()); // normal iteration -- can throw ConcurrentModificationException // may require external synchronization fo...
Hello Stack Overflow! I actually have two questions about Java RMI and thread synchronization: 1) If I implement my RMI remote methods as synchronized, are they guaranteed to be mutually exclusive? I need to make sure that no two of my RMI methods (methods offered to clients) execute at the same time. 2) I have a method that the serve...
I have been studying internals of Java for quite some time. I am curious to learn and understand how threading/locking takes place in Java. So, in order to access a synchronized method or a synchronized block, the thread has to acquire the lock on the object first. So, now, here is what I need a bit more light. So, whenever the thread...
I have two threads that want to synchonize on the same object. Thead A needs to be able to interrupt Thread B if a certain condition has been fullfilled. Here is some pseudo-code of what the two threads do/should do. A: public void run() { while(true) { //Do stuff synchronized(shared) { //Do ...
Hi all, do i need to synchronize this, when many threads accessing the get Method and only one thread is accessing the setList method? public class ListContainer { private List<String> myList = new ArrayList<String(); public List<String> get ( ) { return new ArrayList<String>(myList); } public List<String> set ( ) { ...
Hi. I'm creating a static class which is going to hold some vectors with info. I have to make it synchronized so that the class will be locked if someone is editing or reading from the vectors. What is the best way to do this? Is it enough to have a function which is synchronized inside the class like this: public synchronized insert...
Hello! I'm looking for a text editor that have these 2 features available: - Synchronized scrolling: You can have 2 tabs, side by side and you scroll both at the same time. - Spell check as you type (highlight, underline word, spell check on the fly) I have currently been using Notepad++ exactly because of this feature of Synchronized Sc...
I'm working on a small (java) project where a website needs to maintain a (preferably comma-separated) list of registered e-mail addresses, nothing else, and be able to check if an address is in the list. I have no control over the hosting or the server's lack of database support. Prevayler seemed a good solution, but the website is a g...
Is there any way to block a critical area like with Java synchronized in Django? ...
Hi 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 tha...
i have a (perhaps stupid) question: im using 2 threads, one is writing floats and one is reading this floats permanently. my question is, what could happen worse when i dont synchronize them? it would be no problem if some of the values would not be correct because they switch just a little every write operation. im running the applica...
I have a question. In the following code, if a thread were blocked at wait statement, and another thread attempts to execute foo(), would the hello world message be printed? and Why? synchronized foo(){ system.out.println("hello world"); ..... wait(); ..... } ...
I've heard that choosing to use the word 'synchronized' to describe mutexed statements is simply a mistake (Edit: 'mistake' was a bad choice of words here. Please see edit) in Java, but I'm wondering if there is actually a reason behind the choice. [Edit] Prodded by Safyan's comments, I would like to add that synchronization is a gener...
I have a method shout() with a synchronized block. private void shout(){ System.out.println("SHOUT " + Thread.currentThread().getName()); synchronized(this){ System.out.println("Synchronized Shout" + Thread.currentThread().getName()); try { Thread.sleep(50); } catch (InterruptedException e) { ...
Using Collections class we can make any collection synchronized,immutable or empty what are there respective uses, when we need to implement these type of collections ...
In Java, do ReentrantLock.lock() and ReetrantLock.unlock() use the same locking mechanism as synchronized()? My guess is "No," but I'm hoping to be wrong. Example: Imagine that Thread 1 and Thread 2 both have access to: ReentrantLock lock = new ReentrantLock(); Thread 1 runs: synchronized (lock) { // blah } Thread 2 runs: l...
In Groovy code something simple: #!/usr/bin/env groovy public class test { boolean val def obj=new Object() def dos() { val=false Thread.start() { synchronized(obj) { val=true obj.notifyAll() } } Thread.sleep(5000) synchronized(obj) { while (!val) { obj.wait() } } ...
If I have 2 synchronized methods in the same class, but each accessing different variables, can 2 threads access those 2 methods at the same time? Does the lock occur on the object, or does it get as specific as the variables inside the synchronized method? Example: class x{ private int a; private int b; public synchronize...