JAVA QUESTIONS

What is the difference between sleep(), suspend() and wait() ?

Thread.sleep() takes the current thread to a "Not Runnable" state for specified amount of time. The thread holds the monitors it has acquired. For example, if a thread is running a synchronized block or method and sleep method is called then no other thread will be able to enter this block or method. The sleeping thread can wake up when some other thread calls t.interrupt on it. Note that sleep is a static method, that means it always affects the current thread (the one executing sleep method). A common mistake is trying to call t2.sleep() where t2 is a different thread; even then, it is the current thread that will sleep, not the t2 thread. thread.suspend() is deprecated method. Its possible to send other threads into suspended state by making a suspend method call. In suspended state a thread keeps all its monitors and can not be interrupted. This may cause deadlocks therefore it has been deprecated. object.wait() call also takes the current thread into a "Not Runnable" state, just like sleep(), but with a slight change. Wait method is invoked on a lock object, not thread.

What are the alternatives to Serialization? If Serialization is not used, is it possible to persist or transfer an object using any other approach?

In case, Serialization is not used, Java objects can be serialized by many ways, some of the popular methods are listed below:

·        Saving object state to database, this is most common technique used by most applications. You can use ORM tools (e.g. hibernate) to save the objects in a database and read them from the database.

·        Xml based data transfer is another popular mechanism, and a lot of XML based web services use this mechanism to transfer data over network. Also a lot of tools save XML files to persist data/configurations.

·        JSON Data Transfer - is recently popular data transfer format. A lot of web services are being developed in JSON due to its small footprint and inherent integration with web browser due to JavaScript format.   

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