Skip to main content

Factory Pattern


  • This pattern is used when it must be decided at run time which one of several compatible classes is to be instantiated.
  • For example, the abstract Collator class's getInstance() method returns a collation object that is appropriate for the default locale, as determined by java.util.Locale.getDefault():
  • Like other locale-sensitive classes, you can use the static factory method, getInstance, to obtain the appropriate Collator object for a given locale. 
  • The following example shows how to compare two strings using the Collator for the default locale.
  • Compare two strings in the default locale
    • Collator myCollator = Collator.getInstance();
    • if( myCollator.compare("abc", "ABC") < 0 )
    • System.out.println("abc is less than ABC");
    • else
    • System.out.println("abc is greater than or equal to ABC");
Labels:

Popular posts from this blog

Primitive Obsession with Example

Primitive Obsession is the name of a code smell that occurs when we use primitive data types to represent domain ideas. For example, we use a string to represent a message or an integer to represent an amount of money. For Example: Code with Primitive Obsession // primitiveObsession.java public class primitiveObsession { public static void main ( String args []) { Integer [] cityPopulations = { 13000000 , // London 21903623 , // New York 12570000 , // Tokyo 1932763 , // Stockholm 1605602 , // Barcelona 4119190 // Sydney }; for ( Integer cityPopulation : cityPopulations ) { System . out . println ( cityPopulation ); } } } public class City { private final String name ; private final int population ; private final Continent continent ; public String getName () { return name ; } public int getPopulation () { return population ; } public Continent ge...
Read more

Singleton Pattern

Lazy Initialization :- The instantiation of an object can be delayed until it is actually needed. Usage: This especially beneficial when the constructor is doing a costly job like, accessing a remote database. Example: This code demonstrates how the Singleton pattern can be used to create a counter to provide unique sequential numbers, such as might be required for use as primary keys in a Database:   Sequence.java   public class Sequence { private static Sequence instance; private static int counter; private Sequence() { counter = 0; // May be necessary to obtain // starting value elsewhere... } public static synchronized Sequence getInstance() { if(instance==null) // Lazy instantiation { instance = new Sequence(); } return instance; } public static synchronized int getNext() { return ++counter; } }   Some things to note about this implementation: Synchronized methods are used to ensure that the class is thread-safe. This class cannot be subclassed because the constructor is private ...
Read more