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

static block is here to allow for init invocation. Other way to code it could be eg like this (which to prefer is a matter of taste)

public class Map_en_US extends mapTree {

    private static
            /* thread safe without final,
               see VM spec 2nd ed 2.17.15 */
            Map_en_US m_instance = createAndInit();

    private Map_en_US() {}

    public static Map_en_US getInstance(){
        return m_instance;
    }

    @Override
    protected void init() {
        //some code;
    }

    private static Map_en_US createAndInit() {
        final Map_en_US tmp = new Map_en_US();
        tmp.init();
        return tmp;
    }
}

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update corrected per VM spec 2.17.5, details in comments