随笔档案

public class MainApplication {
    private Properties props;

    private CustomerDatabase custDB;

    public synchronized CustomerDatabase createDBFacade() {
        if (custDB == null) {
            try {
                String dbClassName = props.getProperty("db.class",
                        "com.wci.app.StubCustomerDB");
                Class cls = Class.forName(dbClassName);
                custDB = (CustomerDatabase) cls.newInstance();
            } catch (ClassNotFoundException ex) {
                // ...
            } catch (InstantiationException ex) {
                // ...
            } catch (IllegalAccessException ex) {
                // ...
            }
        }
        return custDB;
    }
}