A: Here the method for getting the reference to the SingleTon object is correct.
B: The constructor should be private
C: The constructor should be private
Note: Java has several design patterns Singleton Pattern being the most commonly used. Java Singleton pattern belongs to the family of design patterns, that govern the instantiation process. This design pattern proposes that at any time there can only be one instance of a singleton (object) created by the JVM.
The class's default constructor is made private, which prevents the direct instantiation of the object by others (Other Classes). A static modifier is applied to the instance method that returns the object as it then makes this method a class level method that can be accessed without creating an object.
OPTION A == SHOW THE LAZY initialization WITHOUT DOUBLE CHECKED LOCKING TECHNIQUE ,BUT
ITS CORRECT OPTION D == Serialzation and thraead-safety guaranteed and with couple of line of code enum Singleton pattern is best way to create Singleton in Java 5 world.
AND THERE ARE 5 WAY TO CREATE SINGLETON CLASS IN JAVA 1>>LAZY LOADING (initialization) USING SYCHRONIZATION 2>>CLASS LOADING (initialization) USING private static final Singleton instance = new
Singleton(); 3>>USING ENUM 4>>USING STATIC NESTED CLASS
5>>USING STATIC BLOCK
AND MAKE CONSTRUCTOR PRIVATE IN ALL 5 WAY.