The keyword synchronized is known to make sure the synchronization of threads within a process in Java. However, care should be taken when writing a thread-safe class to defend itself from possible denial-of-service attack
[[Effective Java| http://books.google.com/books?id=ZZOiqZQIbRMC&pg=PA210&lpg=PA210&dq=private+lock+object+idiom&source=bl&ots=UZP26thN4-&sig=QCPUutihieMlD8cNJIwPLpvBCXc&hl=en&ei=RJPzSsG0EJXilAezjuWjAw&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAgQ6AEwAA#v=onepage&q=private%20lock%20object%20idiom&f=false
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