Singleton instantiation

Question

Below show is the creation on the singleton object.

public class Map_en_US extends mapTree {

    private static Map_en_US m_instance;

    private Map_en_US         


        

Answer 1

If you initialize in the getInstance() method, you can get a racing conditions, i.e. if 2 threads execute the if(m_instance == null) check simulataneously, both might see the instance be null and thus both might call m_instance = new Map_en_US();

Since the static initializer block is executed only once (by one thread that is executing the class loader), you don't have a problem there.

Here's a good overview.