notify

Concept behind putting wait(),notify() methods in Object class [duplicate]

由 半腔热情 提交于 2019-11-27 04:58:50
问题 This question already has answers here : How can the wait() and notify() methods be called on Objects that are not threads? (9 answers) Closed 2 years ago . I am just having hard time to understand concept behind putting wait() in Object class. For this questions sake consider if wait() and notifyAll() are in Thread class. class Reader extends Thread { Calculator c; public Reader(Calculator calc) { c = calc; } public void run() { synchronized(c) { //line 9 try { System.out.println("Waiting

Java Delay/Wait

由 被刻印的时光 ゝ 提交于 2019-11-27 03:14:59
问题 How do I delay a while loop to 1 second intervals without slowing down the entire code / computer it's running on to the one second delay (just the one little loop). 回答1: Thread.sleep(1000); // do nothing for 1000 miliseconds (1 second) 回答2: It seems your loop runs on Main thread and if you do sleep on that thread it will pause the app (since there is only one thread which has been paused), to overcome this you can put this code in new Thread that runs parallely try{ Thread.sleep(1000);

ListView adapter data change without ListView being notified

由 纵饮孤独 提交于 2019-11-27 02:55:39
问题 I've written a ListActivity that has a custom list adapter. The list is being updated from a ContentProvider when onCreate is run. I also have a service that gets started when I run the app and it first updates the ContentProvider, then sends a Broadcast that the content has been updated. My ListActivity receives the broadcast and tries to update my ListView. My problem is, I'm getting intermittent errors about the ListView adapter data changing without the ListView being notified. I call the

ClassCastException with ListView when executing notifyDataSetChanged

由 末鹿安然 提交于 2019-11-27 01:28:09
问题 I have added a view to the header of listVivew, View TopSearch = (View) View.inflate(this, R.layout.search, null); lv.addHeaderView(TopSearch, null, false); And everything is fine until I try to execute (when data changes) adapter.notifyDataSetChanged(); That always crash my application giving me following error: > java.lang.ClassCastException: android.widget.HeaderViewListAdapter If I remove header view then there is no error. Any suggestions? Thanks. 回答1: It seems that whenever you use

running 3 threads in sequence java

由 别来无恙 提交于 2019-11-27 01:12:35
I have 3 threads 1st printing A 2nd printing B 3rd printing C I want to print in sequence A B C A B C A B C and so on..... So I wrote the program below, but I am not able to achieve the same. I am aware of the problem that when status=1 at that time say for example B1 and C1 thread are waiting and when I do notifyAll() both waiting thread wake up and depending on CPU allocation it might print B or C. in this case I want only B to be printed after A. what modification I need to do. public class NotifyAllExample { int status=1; public static void main(String[] args) { NotifyAllExample

Why does notifyAll() raise IllegalMonitorStateException when synchronized on Integer?

由 房东的猫 提交于 2019-11-27 01:01:51
问题 Why does this test program result in a java.lang.IllegalMonitorStateException ? public class test { static Integer foo = new Integer(1); public static void main(String[] args) { synchronized(foo) { foo++; foo.notifyAll(); } System.err.println("Success"); } } Result: Exception in thread "main" java.lang.IllegalMonitorStateException at java.lang.Object.notifyAll(Native Method) at test.main(test.java:6) 回答1: You have noted correctly that notifyAll must be called from a synchronized block.

MySQL listen notify equivalent

由 核能气质少年 提交于 2019-11-26 23:20:53
问题 Is there an equivalent of PostgresQL's notify and listen in MySQL? Basically, I need to listen to triggers in my Java application server. 回答1: No, there aren't any built-in functions like these yet. You need to "ping" (every 1-5 seconds) database with selecting with premade flag like "read" 0/1. After SELECT * FROM mytable WHERE read = 0 update it with read = 1 回答2: Ok, so what I found is that you can make UDF functions in mysql that can do anything but need to be written in C/C++. They can

How to observe contentprovider change? android

由 橙三吉。 提交于 2019-11-26 23:08:57
问题 I'v created a Contentprovide and implements it's update() method like this: @Override public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { final SQLiteDatabase db = mHelper.getWritableDatabase(); int count = db.update(InslideDB.FOLDER_TABLE, values, selection, selectionArgs); /* To notify the observer */ this.getContext().getContentResolver().notifyChange(URI, null); return count; } How can I get notified in my appwidget? Thanks! I'm trying this

IllegalMonitorStateException on notify() when synchronized on an Integer

由 笑着哭i 提交于 2019-11-26 22:12:44
问题 I'm new to using wait() and notify() in Java and I'm getting an IllegalMonitorStateException. Main Code public class ThreadTest { private static Integer state = 0; public static void main(String[] args) { synchronized(state) { System.out.println("Starting thread"); Thread t = new Thread(new AnotherTest()); t.start(); synchronized(state) { state = 0; while(state == 0) { try { state.wait(1000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System

Wait and notify in Consumer and Producer Threads

由 非 Y 不嫁゛ 提交于 2019-11-26 17:25:22
问题 Just started learning multi-threading. I have 5 producers and 2 consumers in multiple threads. Basically this program adds 100 items into the queue. The producer will stop adding when the queue size is 100. I would like the consumer to notify the producer when the consumer removes all the items from the queue so that the producer can start adding again. Currently the producer will wait but never gets notified by the consumer. Producer: public class Producer implements Runnable { private
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