Write a Java program to implement Singleton design pattern.

public class Singleton {\n private static Singleton instance;\n private Singleton() {}\n \n public static synchronized Singleton getInstance() {\n if (instance == null) {\n instance = new Singleton();\n }\n return instance;\n }\n}\n\n// Thread-safe lazy initialization:\npublic class Singleton {\n private static volatile Singleton instance;\n private Singleton() {}\n \n public static Singleton getInstance() {\n if (instance == null) {\n synchronized (Singleton.class) {\n if (instance == null) {\n instance = new Singleton();\n }\n }\n }\n return instance;\n }\n}