类实现单例，类实现,public class

类实现单例，类实现,public class

public class Singleton {    private static Singleton istance = null; // riferimento all'istanza    private Singleton() { } // costruttore    public static Singleton getIstance() {        if(istance==null)            synchronized(Singleton.class) {                if(instance == null)                    istance = new Singleton();                }        return istance;    }    public void metodo() { ... }    ....}...Singleton sg1 = Singleton.getIstance(); // Crea l'istanzasg1.metodo();...