How does notify work in java

The wait method causes the current thread to wait until another thread invokes the notify or notifyAll methods for that object. If another thread calls t. StringBuilder is a mutable sequence of characters. StringBuilder is used when we want to modify Java strings in-place. StringBuffer is a thread-safe equivalent similar of StringBuilder. StringBuilder has methods such as append , insert , or replace that allow to modify strings.

String concatenation It can be a bit surprising, but this code actually runs in O N2 time. The reason is that in Java strings are immutable, and as a result, each time you append to the string new string object is created.

Fomat, even considering parsing, and StringBuffer should be around O n. Because strings are immutable in languages like Java and C , everytime two strings are concatenated a new string has to be created, in which the contents of the two old strings are copied. The important thing to know here is. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. How does wait and notify work?

Ask Question. Asked 8 years, 4 months ago. Active 1 year, 4 months ago. Viewed 7k times. Improve this question. Manish Doshi 1, 1 1 gold badge 8 8 silver badges 17 17 bronze badges. Could you share what you have been trying so far and what you would like to achieve? My program works like this, the wait doesn't execute at all. To be able to help you we really need to see some code! Concurrency can be quite subtle. Add a comment. Active Oldest Votes.

Improve this answer. Directly into your inbox, for free. Thank you. Threads are objects so they have lock like other objects. When we use wait and notify in synchronized methods, which lock do we release? This is an excellent article. However, with the above code I get a very orderly production, until the queue is full, and a very orderly consumption, until the queue is empty, and then this repeats.

The example would be much better if the Thread. The critical section synchronized block is simply too large, and by the time the block ends, it repeats immediately and therefore the same thread is likely to reacquire the lock immediately, thus the long strings of production and consumption, without much interleaving.

Move the sleep outside and randomize it, and you will have a much better example. Hi, Thanks for such a wonderful post. To produce or consume they require lock.

Hello Lokesh,my problem is when i run the program post in your blog ,the output is regular,the consumer do not wake up until the queue is full,can you help me? Above output is also a valid output. To have the process interleave at all I needed to add a Thread.

Hi Lokesh, Can u tell me that what r the conditions to get the object lock. Means can we lock the object through synchronised method and what is the role of wait method for getting the objects lock. See i was really devasted and could not understand how to explain this concept in practical scenarios you showed how easily it can be explained. Hello Lokesh, I implemented the code mentioned in the blog and mentioned below is the output I was getting. Now, the question : Q.

So what happens when tProducer. It gets the lock of taskQueue object and starts producing and then releases the lock when wait is called. At this time tConsumer which was was in waiting for the lock of taskQueue object in consume method to get into synchronized block and goes into consuming the item from list and when size is zero it goes into wait and releases the lock and tProducer acquires it and this keeps on going.

Am I correct with this understanding? So rather than creating a new monitor object for this purpose, I used this existing object.

Regarding error, not sure how you have modified the wait and notify calls. Please share the modified code. Firstly thanks for the clearing my doubt. And secondly, I just wrote like this in Producer and Consumer. Thanks for such a quick response and clearing my doubt. To own the monitor of that object, you must synchronize on it.

So if you want to use this. Thanks for the post. It cleared up many of the confusions I had about threading in general. I just have one quick question about the notify method. Is this wrong? Which threads actually get the notification when the notify method is called? Hi Chandan, Thanks for pointing out this typo. Second answer is correct. I have updated the post.

Article is really helpful to understand concepts of java multi threading thread communication. Is there some mechanism possible which can notify to a particular thread only or a particular thread should be invoked. You may try this solution. Is wait directly got link with q object. Thanks a lot….

HI, Thanks for such an wonderful post. But recently, a question asked to my friend. So, can you help me with that. Not with using wait notify both. So, it will be great if you can provide exaple with both. How can the threads decide among themselves? An example could be group of threads one thread processing only a specific type of message watching a message queue. Upon placing a message in queue, producer can notify all consumer threads.