synchronization

Please clarify my queries regarding Singleton and Multithreading: What is the best way to implement Singleton in Java, in a multithreaded environment? What happens when multiple threads try to access getInstance() method at the same time? Can we make singleton's getInstance() synchronized ? Is synchronization really needed, when using Singleton classes? Jeffrey Yes, it is necessary. There are several methods you can use to achieve thread safety with lazy initialization: Draconian synchronization: private static YourObject instance; public static synchronized YourObject getInstance() { if

I am working on a C# API that is used by a variety of consumers. This API provides access to a shared resource (in my case hardware that does serial communication) , that will often have a few different actors trying to use it concurrently. The issue I have is that some of my consumers will want to use this in a multi-threaded environment - each actor works independently and try to use the resource. A simple lock works fine here. But some of my consumers would prefer to use async-await and time-slice the resource. (As I understand it) this requires an asynchronous lock to yield the timeslice

I have javascript function like this: function myFunction(number) { var x=number; ... ... more initializations //here need to wait until flag==true while(flag==false) {} ... ... do something } The problem is that the javascript is stuck in the while and stuck my program. so my question is how can I wait in the middle of the function until flag is true without "busy-wait"? Because javascript in a browser is single threaded (except for webworkers which aren't involved here) and one thread of javascript execution runs to completion before another can run, your statement: while(flag==false) {}

Possible Duplicate: What is the best way to increase number of locks in java Suppose I want to lock based on an integer id value. In this case, there's a function that pulls a value from a cache and does a fairly expensive retrieve/store into the cache if the value isn't there. The existing code isn't synchronized and could potentially trigger multiple retrieve/store operations: //psuedocode public Page getPage (Integer id){ Page p = cache.get(id); if (p==null) { p=getFromDataBase(id); cache.store(p); } } What I'd like to do is synchronize the retrieve on the id, e.g. if (p==null) {