44 lines
1.9 KiB
Markdown
44 lines
1.9 KiB
Markdown
---
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layout: pattern
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title: Factory Method
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folder: factory-method
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permalink: /patterns/factory-method/
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pumlid: NSZB3G8n30N0Lg20n7UwCOxPP9MVx6TMT0zdRgEvjoazYeRrMmMsFuYChtmqr7Y6gycQq8aiQr3hSJ7OwEGtfwBUZfas0shJQR3_G2yMBFkaeQYha4B-AeUDl6FqBm00
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categories: Creational
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tags:
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- Java
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- Difficulty-Beginner
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- Gang Of Four
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---
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## Also known as
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Virtual Constructor
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## Intent
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Define an interface for creating an object, but let subclasses
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decide which class to instantiate. Factory Method lets a class defer
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instantiation to subclasses.
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## Applicability
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Use the Factory Method pattern when
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* a class can't anticipate the class of objects it must create
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* a class wants its subclasses to specify the objects it creates
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* classes delegate responsibility to one of several helper subclasses, and you want to localize the knowledge of which helper subclass is the delegate
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## Known uses
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* [java.util.Calendar](http://docs.oracle.com/javase/8/docs/api/java/util/Calendar.html#getInstance--)
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* [java.util.ResourceBundle](http://docs.oracle.com/javase/8/docs/api/java/util/ResourceBundle.html#getBundle-java.lang.String-)
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* [java.text.NumberFormat](http://docs.oracle.com/javase/8/docs/api/java/text/NumberFormat.html#getInstance--)
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* [java.nio.charset.Charset](http://docs.oracle.com/javase/8/docs/api/java/nio/charset/Charset.html#forName-java.lang.String-)
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* [java.net.URLStreamHandlerFactory](http://docs.oracle.com/javase/8/docs/api/java/net/URLStreamHandlerFactory.html#createURLStreamHandler-java.lang.String-)
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* [java.util.EnumSet](https://docs.oracle.com/javase/8/docs/api/java/util/EnumSet.html#of-E-)
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* [javax.xml.bind.JAXBContext](https://docs.oracle.com/javase/8/docs/api/javax/xml/bind/JAXBContext.html#createMarshaller--)
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## Credits
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* [Design Patterns: Elements of Reusable Object-Oriented Software](http://www.amazon.com/Design-Patterns-Elements-Reusable-Object-Oriented/dp/0201633612)
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