synchronization

Difference between Hashtable and Collections.synchronizedMap(HashMap)

由 牧云@^-^@ 提交于 2019-11-28 03:55:00
As far as I know, java.util.Hashtable synchronizes each and every method in the java.util.Map interface, while Collections.synchronizedMap(hash_map) returns a wrapper object containing synchronized methods delegating calls to the actual hash_map (correct me if I am wrong). I have two questions : What difference does it make to synchronize each and every method and to have a wrapper class? What are the scenarios to choose one over the other? What happens when we do Collections.synchronizedMap(hash_table) ? Will this be equal to simply using a normal java.util.Hashtable ? Nadir Muzaffar Here are

Synchronization on “this” or private Object in Java? [duplicate]

由 ￣綄美尐妖づ 提交于 2019-11-28 03:44:54
问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Avoid synchronized(this) in Java? What is the difference between the two pieces of code ? What are advantages and disadvantages of each? 1) public class Example { private int value = 0; public int getNextValue() { synchronized (this) { return value++; } } } 2) public class Example { private final Object lock = new Object(); private int value = 0; public int getNextValue() { synchronized (lock) { return value++;

OK to copy a CRITICAL_SECTION?

由 痞子三分冷 提交于 2019-11-28 03:28:12
问题 One can use a CRITICAL_SECTION variable to get mutual exclusion. My question is: does CRITICAL_SECTION support copying? If I pass one by value to another thread, can I know for sure that mutual exclusion will work? I wouldn't be surprised if the answer is "you cannot do that", but it'd be nice to have some sort of official confirmation. I wasn't able to find a statement either way in the documentation. 回答1: No. A CRITICAL_SECTION cannot be copied. MSDN states this explicitly: A critical

Android java.lang.IllegalMonitorStateException: object not locked by thread before wait()

由 随声附和 提交于 2019-11-28 03:23:39
问题 I define a global static object as a synchronization lock. public static Object ConfirmationSynObj = new Object(); The following function is what I wrote, but it throw a IllegalMonitorStateException. synchronized (Config.ConfirmationSynObj) { new Thread(new Runnable() { @Override public void run() { //this is a http request appSignInfo = getAPKSignature(context, pkinfo.packageName); Config.ConfirmationSynObj.notify(); } }).start(); try { Config.ConfirmationSynObj.wait(); } catch

Is it well-defined behavior to modify one element of an array while another thread modifies another element of the same array?

由 ▼魔方 西西 提交于 2019-11-28 03:22:54
问题 Given an array of type foo_t[n] and a set of n threads, where each of the n threads reads and modifies a different element of the array, do I need to explicitly synchronize modifications of the array or can I assume that concurrently modifying members of the array is well-defined behavior? Does it matter how large foo_t is / what alignment it has? 回答1: What I try to do is well-defined behavior. See ISO/IEC 9899:2011 §5.1.2.4.27: NOTE 13 Compiler transformations that introduce assignments to a

How to sync with a remote Git repository?

由 这一生的挚爱 提交于 2019-11-28 03:03:23
I forked a project on github, made some changes, so far so good. In the meantime, the repository I forked from changed and I would like to get those changes into my repository. How do I do that ? Generally git pull is enough, but I'm not sure what layout you have chosen (or has github chosen for you). Mark Hibberd Assuming their updates are on master, and you are on the branch you want to merge the changes into. git remote add origin https://github.com/<github-username>/<repo-name>.git git pull origin master Also note that you will then want to push the merge back to your copy of the

Why is Synchronized block better than synchronized method?

由 点点圈 提交于 2019-11-28 02:53:54
I have started learning synchronization in threading. Synchronized method: public class Counter{ private static int count = 0; public static synchronized int getCount(){ return count; } public synchronized setCount(int count){ this.count = count; } } Synchronized block : public class Singleton{ private static volatile Singleton _instance; public static Singleton getInstance(){ if(_instance == null){ synchronized(Singleton.class){ if(_instance == null) _instance = new Singleton(); } } return _instance; } When should I use Synchronized method and Synchronized block ? Why is Synchronized block

Java - synchronizing static methods

由 核能气质少年 提交于 2019-11-28 02:53:52
问题 Here is a piece of text I found at this link. "Avoid lock on static methods The worst solution is to put the "synchronized" keywords on the static methods, which means it will lock on all instances of this class." Why would synchronizing a static method lock all instances of the class? Shouldn't it just lock the Class? 回答1: Here's my test code that shows that you're right and the article is a bit over-cautious: class Y { static synchronized void staticSleep() { System.out.println("Start

Own sync adapter for Android?

由 白昼怎懂夜的黑 提交于 2019-11-28 02:49:15
The press release of Android 2.0 states that the new release supports sync adapters so that emails and calendars cannot only be synced with gmail and exchange. However, there is no information available online how to write such a sync adapter. Has anyone tried it and some example code available? white_gecko These two articles by Sam Steele (January 23rd, 2010) are about the implementation of the last.fm sync adapter. Do not miss the second part and the opensource projects that are mentioned at the end of the articles. http://www.c99.org/2010/01/23/writing-an-android-sync-provider-part-1/ http:

How to identify EKEvent uniquely with Sync across the devices

由 旧巷老猫 提交于 2019-11-28 02:25:28
I am trying to make Event Syncing feature for a Project. I need to sync events with the remote server. Let's say I Installed the App in Device A. If I login to another device lets take B, then events synced from A should also appear in Device B, and events of B should also be synced. Now if I again login into the Device A, Events of B should be added. But events previously from A should not again be added to Device A again For this I decided to keep its eventIdentifier on the remote database. The Issue now happens when I again Go back to Device B, where events previously synced from Device A
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