How to synchronize a method for all instances of a class

Question

Hi,
How to make a method synchronized for all instances of a class? If a simple method is synchronized, then multiple threads cannot access it at the same time. If we make the method as static, then we are making it synchronized at class level.How to make a synchronized method so that no two instances (objects) of a class can access it at the same?
Thanks
Neha

Answer 1

Neha_Khands wrote:
There is nothing wrong with that. Actually this question was asked in an interview. They didnt want to create a static method. They told me that synchronization can be achieved at instance level also. and for that we have to call some Class.getInstance().synchronied method inside constructor. Kind of a dumb question. First, synchronization does not occur "at a class level" or "at an instance level." Syncing is always the same--a single object's lock is obtained, which prevents any other threads from obtaining that lock. The only thing that makes it appear that there are special cases is that declaring a method synchronized obtains the lock associated with the instance or with the Class object for that class. But that's just syntactic sugar. The Class object lock is identical to the instance lock, which in turn is identical to a lock on some other arbitrary Object created just to serve as a lock. There's no such things as "locking the class" or "locking the instance."
Second, and more important, making an instance method synced across all instances is a grotesquely artificial situation, IMHO, and if it were to ever come up, the right way to do it is to have that instance method call a static synchronized method.