class Singleton {

private static Singleton instance = new Singleton();

private Singleton() {

}

public static Singleton getInstance() {

return instance;

}

public void print() {

System.out.println("Hello Singleton...");

}

}

class Singleton {

private static volatile Singleton singleton = null;

private Singleton() {

}

public static Singleton getInstance() {

if (singleton == null) {

synchronized (Singleton.class) {

if (singleton == null) {

singleton = new Singleton();

}

}

}

return singleton;

}

public void print() {

System.out.println("Hello World");

}

}

class Singleton {

private static volatile Singleton singleton = null;

private Singleton() {

}

public static Singleton getInstance() {

if (singleton == null) {

synchronized (Singleton.class) {

if (singleton == null) {

singleton = new Singleton();

}

}

}

return singleton;

}

public void print() {

System.out.println("Hello World");

}

}

class Singleton {

private static volatile Singleton singleton = null;

private Singleton() {

}

public static Singleton getInstance() {

if (singleton == null) {

synchronized (Singleton.class) {

if (singleton == null) {

singleton = new Singleton();

}

}

}

return singleton;

}

public void print() {

System.out.println("Hello World");

}

}

class Singleton {

private static volatile Singleton singleton = null;

private Singleton() {

}

public static Singleton getInstance() {

if (singleton == null) {

synchronized (Singleton.class) {

if (singleton == null) {

singleton = new Singleton();

}

}

}

return singleton;

}

public void print() {

System.out.println("Hello World");

}

}

class Singleton {

private static volatile Singleton singleton = null;

private Singleton() {

}

public static Singleton getInstance() {

if (singleton == null) {

synchronized (Singleton.class) {

if (singleton == null) {

singleton = new Singleton();

}

}

}

return singleton;

}

public void print() {

System.out.println("Hello World");

}

}