Would synchronising on class object block the entire class (and its members) [duplicate]

Question

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is synchronized by class name in a function will be valid across extended classes? (3 answers)

Closed 8 years ago.

Would this block all access to Foo and its static members while the statements in the class is executing?

MyBlock:
synchronize(Foo.class)
{
    // ... do something 
}

In other words, while MyBlock is executing, no other thread would be able to call any static methods in Foo, right?

Ok, if this does not do it. Then how do I stop a class and its members from being accessed for a certain amount of time? Thanks

Answer 1

No. The use of the lock object itself, the Foo.class object in this case, is unaffected by synchronized blocks using it as a lock object.

You can't stop classes from using being used, unless you put them behind something like a proxy that controls access, or make the methods themselves conditionally block execution internally, which doesn't really prevent access but simulates it.

Answer 2

If you want to lock on static members, you can define a dummy static member to wich you can lock, and every time you want to access the static members, you'll just check if that dummy member is locked.

class Foo{
     public static Integer dummyLock;
....
}

afterwhich you can: MyBlock:

synchronize(Foo.dummyLock)
{
    // ... access static members here
}