On Thu, Apr 28, 2011 at 6:13 PM, Uwe Schindler <[email protected]> wrote:
> In general a *newly* created object that was not yet seen by any other
> thread is always safe. This is why I said, set all bits in the ctor. This is
> easy to understand: Before the ctor returns, the object's contents and all
> references like arrays are not seen by any other thread (that's guaranteed).
Section 17.5 of the JLS gives the following example:
class FinalFieldExample {
final int x;
int y;
static FinalFieldExample f;
public FinalFieldExample() {
x = 3;
y = 4;
}
static void writer() {
f = new FinalFieldExample();
}
static void reader() {
if (f != null) {
int i = f.x; // guaranteed to see 3
int j = f.y; // could see 0
}
}
}
Essentially, there is no guarantee that the work in the constructor
has been completed when another thread gets a reference to the object.
To make the guarantee, use the final keyword.
It seems like this contradicts the claim above, but maybe I'm missing something.
TX
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