synchronization

问题 I need to store the result of FireBase getValue method that is async by his own. I can\'t use something like \"onPostExecute()\" and, for my purpose, i can\'t execute all my operation \"into onDataChange()\" because i need some references in future time in other activities. Here my snippet to retrieve data: List<Village> villages = new LinkedList<>(); Firebase ref = new Firebase(\"MYFIREBASEURL\").child(\"village\"); ref.addValueEventListener(new ValueEventListener() { @Override public void

问题 How do atomic / volatile / synchronized work internally? What is the difference between the following code blocks? Code 1 private int counter; public int getNextUniqueIndex() { return counter++; } Code 2 private AtomicInteger counter; public int getNextUniqueIndex() { return counter.getAndIncrement(); } Code 3 private volatile int counter; public int getNextUniqueIndex() { return counter++; } Does volatile work in the following way? Is volatile int i = 0; void incIBy5() { i += 5; } equivalent

问题 Whenever a question pops up on SO about Java synchronization, some people are very eager to point out that synchronized(this) should be avoided. Instead, they claim, a lock on a private reference is to be preferred. Some of the given reasons are: some evil code may steal your lock (very popular this one, also has an \"accidentally\" variant) all synchronized methods within the same class use the exact same lock, which reduces throughput you are (unnecessarily) exposing too much information

问题 This question already has answers here : JavaScript closure inside loops – simple practical example (44 answers) Closed last year . I am running an event loop of the following form: var i; var j = 10; for (i = 0; i < j; i++) { asynchronousProcess(callbackFunction() { alert(i); }); } I am trying to display a series of alerts showing the numbers 0 through 10. The problem is that by the time the callback function is triggered, the loop has already gone through a few iterations and it displays a

问题 In my code I have a loop that waits for some state to be changed from a different thread. The other thread works, but my loop never sees the changed value. It waits forever. However, when I put a System.out.println statement in the loop, it suddenly works! Why? The following is an example of my code: class MyHouse { boolean pizzaArrived = false; void eatPizza() { while (pizzaArrived == false) { //System.out.println(\"waiting\"); } System.out.println(\"That was delicious!\"); } void