Java – Singleton Pattern

Singleton Pattern: Ensure that only one instance of the class exists.

Provide global access to that instance by:

1. Declaring all constructors of the class to be private.
2. Providing a static method that returns a reference to the instance. The lazy initialization concept is used to write the static methods.
3. The instance is stored as a private static variable.

class Printer {             private static Printer printer = new Printer();             private Printer()             {                         // empty             }             public static Printer getPrinter()             {                         return printer;             }             void takePrints()             {                         System.out.println(“Printing…”);             } } class UsePrinter {             public static void main(String[] args)             {                         Printer printer = Printer.getPrinter();                         printer.takePrints();             } }

Note: We need to synchronize takePrints() method of Printer class when multiple threads trying take prints parallel.