■ synchronized can only appear on a method, or on a code block, or as a statement.
■ You cannot successfully synchronize on a local variable. Only objects can have locks. And every thread has its own copy of local variables anyway.
■ When synchronized is used on a method, the object reference is this.
■ Two ways to release synchronized. Either:
(1) the code exits,or
(2) wait( ) is called.
■ Overriding subclasses can ignore any synchronized appearing on a method being overridden.