Java – Singleton Desing Pattern

public class UserKatalog {

private static UserKatalog instance;

private static Object lock=new Object();

private UserKatalog()
{
System.out.println("UserKatalog singleton nesnesi olusturuldu");
}

public static UserKatalog getInstance()
{
if(instance==null)
{
synchronized (lock) {

if(instance==null)
{
return new UserKatalog();
}
}
}
return instance;

}
}

public class Test {

public static void main(String[] args) {
UserKatalog.getInstance();
}
}

Ekran çıktısı
UserKatalog singleton nesnesi olusturuldu