wait() forces the thread to release its lock. This means that it must own the lock of an object before calling the wait() method of that (same) object. Hence the thread must be in one of the object’s synchronized methods or synchronized block before calling wait().
Why wait and notify method are called from synchronized block?
The wait() is called, so that the thread can wait for some condition to occur when this wait() call happens, the thread is forced to give up its lock. To give up something, you need to own it first. Thread needs to own the lock first. Hence the need to call it inside a synchronized method/block.
What is the purpose of the wait () notify () and notifyAll () methods in Java?
The wait() method causes the current thread to wait until another thread invokes the notify() or notifyAll() methods for that object. The notify() method wakes up a single thread that is waiting on that object’s monitor. The notifyAll() method wakes up all threads that are waiting on that object’s monitor.
Can we use wait and notify without synchronized?
If you need to call wait(), notify(), or notifyAll() from within a non-synchronized method, then you must first obtain a lock on the object’s monitor. If you don’t, an exception will be generated when an attempt is made to call the method in question.
Why wait () notify () and notifyAll () methods are defined in object class not thread class?
If wait() and notify() were on the Thread instead then each thread would have to know the status of every other thread and there is no way to know thread1 that thread2 was waiting for any resource to access. Hence, notify, wait, notifyAll methods are defined in object class in Java.
What happens if notify () is called and no thread is in waiting state?
PS: Notify will never invoke the other waiting thread immediately. It will just remove a thread from Wait Set and then this thread will be invoked by the Operating System!
How do you use a synchronized block?
Same Example of synchronized block by using annonymous class:
- class Table{
- void printTable(int n){
- synchronized(this){//synchronized block.
- for(int i=1;i<=5;i++){
- System.out.println(n*i);
- try{
- Thread.sleep(400);
- }catch(Exception e){System.out.println(e);}
Why do we need the wait () and notify () methods?
We wait on an object if we are waiting for some condition to change – some resource to become available. We notify on an object if we want to awaken sleeping threads. There can be any number of lock objects in your program – each locking a particular resource or code segment.
What notifyAll () method does?
notifyAll() wakes up all threads that are waiting on this object’s monitor. A thread waits on an object’s monitor by calling one of the wait methods. … This method should only be called by a thread that is the owner of this object’s monitor.
What is SwingUtilities invokeLater () used for?
An invokeLater() method is a static method of the SwingUtilities class and it can be used to perform a task asynchronously in the AWT Event dispatcher thread. The SwingUtilities. invokeLater() method works like SwingUtilities. invokeAndWait() except that it puts the request on the event queue and returns immediately.
Why sleep () is static method?
So since the only thread worth calling yield on is the current thread, they make the method static so you won’t waste time trying to call yield on some other thread. This is because whenever you are calling these methods, those are applied on the same thread that is running.
What is wait () in Java?
The java. lang. Object. wait() causes current thread to wait until another thread invokes the notify() method or the notifyAll() method for this object. … This method should only be called by a thread that is the owner of this object’s monitor.
What is the difference between wait () notify () and notifyAll ()?
notify() and notifyAll() methods with wait() method are used to for communication between the threads. … But when we use notifyAll() method then multiple threads got the notification but execution of threads will be performed one by one because thread requires lock and only one lock is available for one object.