Design Patters: Strategy
Credit: Concepts explained here are based on a book, “増補改訂版Java言語で学ぶデザインパターン入門”. A strategy pattern makes it easy to change an algorithm to solve a problem. Let’s run a sample program which uses two different strategies for Rock paper scissors. Hand: A class representing a hand, one of Rock, Paper and Scissors. Strategy: A class representing strategy…
Design Patters: Bridge
Credit: Concepts explained here are based on a book, “増補改訂版Java言語で学ぶデザインパターン入門”. A bridge pattern builds a bridge between two kinds of classes: one working as abstraction and one working as implantation. Let’s see a concrete example. Display and CountDisplay work as abstraction or User Interface. These classes delegate actual work to a class working as implementation.…
Design Patters: Abstract Factory
Credit: Concepts explained here are based on a book, “増補改訂版Java言語で学ぶデザインパターン入門”. In an abstract factory pattern, different abstract components are combined to create an abstract product. Let’s see a sample program which creates a HTML file. There are two packages: factory package and listfactory package. A factory package contains classes that create an abstract factory, components…
Design Patters: Builder
Credit: Concepts explained here are based on a book, “増補改訂版Java言語で学ぶデザインパターン入門”. A builder pattern is a pattern in which an instance is created by calling a class which in turn calls an interface which is a framework for objects to be built. Let’s create a sample program in which a document is created. A document is…
Design Patters: Prototype
Credit: Concepts explained here are based on a book, “増補改訂版Java言語で学ぶデザインパターン入門”. Prototype is a pattern in which an instance is duplicated by calling an Interface, not by calling a constructor. This pattern is used when it is convenient to clone an instance than to create a new instance. Let’s explain concepts in a program. First, we…
Design Patters: Singleton
Credit: Concepts explained here are based on a book, “増補改訂版Java言語で学ぶデザインパターン入門”. In this blog post, a singleton pattern is explained. This pattern is used when you want to guarantee that there are no more than one instance generated. A singleton class creates an instance by being called get_instance method. Note that since Python does not have…
Design Patters: Factory Method
(Credit: Concepts explained here are based on a book, “増補改訂版Java言語で学ぶデザインパターン入門”.) A factory method pattern is a pattern in which a superclass describes how an instance should be created but does not define its internal structure. Its detailed structure is written in a subclass. Let’s create a program. In this program, a framework package is used…
Design Patters: Template Method
A template method pattern is a pattern that has a template. In this pattern, a superclass has template methods which have some abstract methods. These methods describe how abstract methods are called which are implemented by its subclasses. Let’s see an example by creating a program which displays characters or strings for five times. Class…
Design Patterns: Adapter
In this post, an adapter pattern is explained. Original code in Java can be found in a book, I “増補改訂版Java言語で学ぶデザインパターン入門”. An adapter works as a middleware between an adaptee and a target, each has its own methods. If an adaptee and a target are incompatible with each other, an adapter bridges a gap between the…
Design Patterns: Iterator
In this blog post, I am going to explain one of the design patterns, an iterator. Wikipedia defines an iterator this way: An iterator is an object that enables a programmer to traverse a container, particularly lists. I explain concepts based on a book, “増補改訂版Java言語で学ぶデザインパターン入門”. I translate code in Java in the book to code in Python. In this…
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