Java singleton design pattern example

//Singleton design pattern - example class //Eager initialization public class SingletonObject {             //Our static variable holding an instance of an existing singleton class        private static SingletonObject singletonObject;              static {          // Initialize "singletonObject" only once          singletonObject = new SingletonObject();        }             //The class constructor method is also private. We can not create the class instance outside of this class        private SingletonObject() {               //...constructor codes        }             //The method that returns the single instance of the SingletonObject class        public static SingletonObject getInstance() {               return singletonObject;        }        //Prevent cloning of class by throwing CloneNotSupportedException        @Override        public Object clone() throws CloneNotSupportedException {               throw new CloneNotSupportedException();        } }

//Singleton design pattern - example class //Lazy initialization public class SingletonObject {             //Our static variable holding an instance of an existing singleton class        private static SingletonObject singletonObject = null;              //The class constructor method is also private. We can not create the class instance outside of this class        private SingletonObject() {               //...constructor codes        }             //The method that returns the single instance of the SingletonObject class        public static SingletonObject getInstance() {           if(singletonObject == null) {                  synchronized (SingletonObject.class) {                         //double-checked locking                         if(singletonObject == null) {                               singletonObject = new SingletonObject();                         }                  }                             }               return singletonObject;        }        //Prevent cloning of class by throwing CloneNotSupportedException        @Override        public Object clone() throws CloneNotSupportedException {               throw new CloneNotSupportedException();        } }