Question

I was wondering, whether the following code are safe.

public class GUIBundle {

    // The technique known as the initialization on demand holder idiom, 
    // is as lazy as possible.
    // http://en.wikipedia.org/wiki/Initialization_on_demand_holder_idiom
    //private static class BundleHolder {
    //    private static final ResourceBundle bundle = ResourceBundle.getBundle("org.yccheok.jstock.data.gui");
    //}
    private static final ResourceBundle bundle = ResourceBundle.getBundle("org.yccheok.jstock.data.gui");

    private GUIBundle() {
    }

    public static String getString(String key) {
        // return BundleHolder.bundle.getString(key);
        return bundle.getString(key);
    }
}

---

public class SellPortfolioChartJDialog extends javax.swing.JDialog {

    private static final String[] cNames = new String[] {
        GUIBundle.getString("BuyPortfolioTreeTableModel_NetGainValue")
    };
}

---

Since cNames is within static scope, is it safe for it to access static bundle? Does it make any different whether I am using lazy initialization technique?

I remember I came across an article (I lost the article anyway) talking about nondeterministic of initialization order of static variables. I am not sure whether the nondeterministic of initialization order of static variables, applied to the above case?

Answer 1

I believe the nondeterministic initialization order of static variables (in different compilation units) is a C/C++ “feature”. In Java, static variables are initialized when their class is loaded, and within a single class in their order of declaration. So the order is deterministic (at least in a single threaded environment).

This guarantees that what you intend to do should work: when GUIBundle is first referenced, the classloader loads it and initializes bundle too. The call to GUIBundle.getString() happens only after the class initialization is done.