Re: Check if a final field is initialized

"Daniel Dyer" <"You don't need it">
Tue, 23 Jan 2007 22:00:06 -0000
On Tue, 23 Jan 2007 21:54:02 -0000, Stefan Z Camilleri <
m> =



I am creating a singleton that shall be accessed by multiple threads, =


possibly simultaneously... here is my code

public class FooEngine implements FooInterface {

    private static final m_barElement;

    public static FooInterface getBarInstance() {

        synchronized (BarElement) {
            if (null == m_barElement) m_barElement = new FooEngine();

        return m_barElement;

Somehow I need to check if m_barElement is initialized... in C# I =

generally check for null, yet in Java it seems as though I have to =

explicitly initialize it to null... but this would then mean that I =

cannot assign it to an instance later.

Setting it to an instance of FooEngine at declaration is not an option=


since FooEngine requires lots of other preparatory work prior to it's =


being instantiated.

But it will not be instantiated until the class is loaded. Classes in =

Java aren't loaded until they are needed, so you effectively get lazy =

initialisation for free. Unless there are other static members of the =

class that are accessed before the call to getBarInstance(), the class =

won't be loaded until the point at which the getBarInstance() invocation=



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