#flyweight pattern java

[codeonedigest]

What is Flyweight design pattern? | Complete Tutorial with Java Examples

Full Video Link https://youtu.be/w2JitxSYMhc Hello friends, a new #video on #flyweight #design #pattern with #Java #example is published on #codeonedigest #youtube channel. Ultimate guide to flyweight #java design pattern. #flyweightdesignpattern #javade

What is Flyweight Design Pattern? Flyweight pattern provides a mechanism by which you can avoid creating a large number of ‘expensive’ objects and instead reuse existing instances to represent new ones. Flyweight pattern is useful in optimising the creation of too many objects by reusing the common data. Flyweight pattern reduce the creation of objects by sharing data, decrease memory footprint…

[codezup]

Optimizing Object Creation with Flyweight Pattern in Java

Optimizing Object Creation with the Flyweight Pattern in Java 1. Introduction 1.1 Brief Explanation The Flyweight pattern is a structural design pattern that aims to minimize memory usage and improve performance by sharing common data between multiple objects. It is particularly useful when dealing with large numbers of objects that have common state, such as characters in a text editor, or…

[simplexianpo]

Java : Flyweight Pattern design followed by Integer cache

Test code:

  public static void main(String[] args) {

    Integer i1 = 127;

    Integer i2 = 127;

    System.out.println(i1 == i2);

    Integer i3 = 128;

    Integer i4 = 128;

    System.out.println(i3 == i4);

}

Output result:

true

false

  There is a flyweight pattern design (cache) in the packaging class: the commonly used numbers are stored in the constant pool, and each time they are obtained directly from the constants, there is no need to create them again-> to improve efficiency

 Byte、Short、Integer、Long : Share the same object between [-128,127]

Character : Share the same object between [0,127]

That is, look for it from the cache first, and return it directly after finding it, without opening up new space

 **Note: every time new is a new memory space, compare memory addresses**

 ####View Java source code:

     private static class IntegerCache {

       static final int low = -128;

       static final int high;

       static final Integer cache[];

         static {

           // high value may be configured by property

           int h = 127;

           String integerCacheHighPropValue =

               sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");

           if (integerCacheHighPropValue != null) {

               try {

                   int i = parseInt(integerCacheHighPropValue);

                   i = Math.max(i, 127);

                   // Maximum array size is Integer.MAX_VALUE

                   h = Math.min(i, Integer.MAX_VALUE - (-low) -1);

               } catch( NumberFormatException nfe) {

                   // If the property cannot be parsed into an int, ignore it.

               }

           }

           high = h;

             cache = new Integer[(high - low) + 1];

           int j = low;

           for(int k = 0; k < cache.length; k++)

               cache[k] = new Integer(j++);

             // range [-128, 127] must be interned (JLS7 5.1.7)

           assert IntegerCache.high >= 127;

       }

         private IntegerCache() {}

   }

[ageloire]

The Beginner's Guide to Design Patterns

To fully understand the importance of design patterns, let's start with an example -- when a user uses your product, how do they save their landing page, blog post, template, etc.? Do their projects auto-save, or do they need to press a "Save" button?

Let's say you choose auto-save. Great. Now, how much time do you have? Do you want to go into each individual page and code for the auto-save component, with a big potential for error?

Or do you want to use a design pattern to ensure each of your website pages saves the same way, without tedious effort on your part?

That's the value of design patterns.

Here, we'll explain what design patterns are, and provide lists of design patterns in Java, C# and .Net, so you can save valuable time and effort on your next design project.

Design patterns explained simply

At its most basic, design patterns are solutions to recurring problems.

In the UX world, then, a design pattern is a pre-prescribed solution to a common design problem. Essentially, it's a way of saying, "Here's how we typically solve for this problem, if you want to use our method."

Chelsea Bathurst, a Design Lead at HubSpot, puts it this way: "Basically, components are the foundation -- how does this thing look. Design patterns are how they work together."

Design patterns are undeniably useful. They allow designers to avoid "re-inventing the wheel", and because they are tried-and-true solutions from experienced designers, they are less risky than creating something from scratch.

There are three types of design patterns: 

Creational design patterns: Regarding object creation mechanisms

Structural design patterns: Regarding Class and Object composition -- identifying relationships and patterns between components

Behavioral design patterns: Identifying communication patterns between Class objects

Next, let's take a look at our lists of design patterns in java, or C# and .NET, so you can begin applying them yourself. 

Design patterns in Java

Factory Pattern

Abstract Factory Pattern

Singleton Pattern

Prototype Pattern

Builder Pattern

Adapter Pattern

Bridge Pattern

Composite Pattern

Decorator Pattern

Facade Pattern

Flyweight Pattern

Proxy Pattern

Chain Of Responsibility Pattern

Command Pattern

Interpreter Pattern

Iterator Pattern

Mediator Pattern

Memento Pattern

Observer Pattern

State Pattern

Strategy Pattern

Template Pattern

Visitor Pattern

Design patterns in C# and .NET

Abstract Factory Pattern

Builder Pattern

Factory Method Pattern

Prototype Pattern

Singleton Pattern

Adapter Pattern

Bridge Pattern

Composite Pattern

Decorator Pattern

Facade Pattern

Flyweight Pattern

Proxy Pattern

Chain Of Responsibility Pattern

Command Pattern

Interpreter Pattern

Iterator Pattern

Mediator Pattern

Memento Pattern

Observer Pattern

State Pattern

Strategy Pattern

Template Pattern

Visitor Pattern

Once you understand the uses of each of these design patterns, you can choose which ones will best fit your needs. However, it's critical you understand basic java, or C# and .NET programming concepts, to correctly apply these solutions. If you don't, begin by taking an introductory course before taking any next steps with these design patterns.

from Marketing https://blog.hubspot.com/marketing/design-patterns

[lewiskdavid90]

80% off #From 0 to 1: Design Patterns – 24 That Matter – In Java – $10

An intensely practical, deeply thoughtful and quirky look at 24 Design Patterns. Instructors are ex-Google, Stanford.

All Levels,  – 11.5 hours,  63 lectures 

Average rating 4.2/5 (4.2 (100 ratings) Instead of using a simple lifetime average, Udemy calculates a course’s star rating by considering a number of different factors such as the number of ratings, the age of ratings, and the likelihood of fraudulent ratings.)

Course requirements:

There are no pre-requisites other than curiosity – about Design, about Patterns, about Life

Course description:

Prerequisites: Basic understanding of Java Taught by a Stanford-educated, ex-Googler, husband-wife team More than 50 real-world examples

This is an intensely practical, deeply thoughtful, and quirky take on 24 Design Patterns that matter.

Let’s parse that.

The course is intensely practical, bursting with examples – the more important patterns have 3-6 examples each. More than 50 real-world Java examples in total. The course is deeply thoughtful, and it will coax and cajole you into thinking about the irreducible core of an idea – in the context of other patterns, overall programming idioms and evolution in usage. The course is also quirky. The examples are irreverent. Lots of little touches: repetition, zooming out so we remember the big picture, active learning with plenty of quizzes. There’s also a peppy soundtrack, and art – all shown by studies to improve cognition and recall. Lastly, the patterns matter because each of these 24 is a canonical solution to recurring problems.

What’s Covered:

Decorator, Factory, Abstract Factory, Strategy, Singleton, Adapter, Facade, Template, Iterator, MVC, Observer, Command, Composite, Builder, Chain of Responsibility, Memento, Visitor, State, Flyweight, Bridge, Mediator, Prototype, Proxy, Double-Checked Locking and Dependency Injection. The only GoF pattern not covered is the Interpreter pattern, which we felt was too specialized and too far from today’s programming idiom; instead we include an increasingly important non-GoF pattern, Dependency Injection. Examples: Java Filestreams, Reflection, XML specification of UIs, Database handlers, Comparators, Document Auto-summarization, Python Iterator classes, Tables and Charts, Threading, Media players, Lambda functions, Menus, Undo/Redo functionality, Animations, SQL Query Builders, Exception handling, Activity Logging, Immutability of Strings, Remote Method Invocation, Serializable and Cloneable, networking. Dependency Inversion, Demeter’s Law, the Open-Closed Principle, loose and tight coupling, the differences between frameworks, libraries and design patterns.

Talk to us!

Mail us about anything – anything! – and we will always reply

Full details Identify situations that call for the use of a Design Pattern Understand each of 24 Design Patterns – when, how, why and why not to use them Distill the principles that lie behind the Design Patterns, and apply these in coding and in life, whether or not a Design Pattern is needed Spot programming idioms that are actually built on Design Patterns, but that are now hiding in plain sight

Full details Yep! Engineers – from street-smart coders to wise architects – ought to take this course. After this class, you’ll look at software design with a new pair of eyes. Yep! Product Managers ought to take this course – you will learn to understand the ‘how’ of Software Design without being constrained by it. Yep! Technology executives and investors who don’t write code ought to take this course – after this you will always have an intelligent point-of-view on software, and won’t find your eyes glazing over when its time to talk nitty-gritty Computer Science majors (undergrad or grad) – if you are among the folks that make ‘real world example Observer Pattern’ such a common search phrase on Google, this is precisely the place for you. Yep! Journalists, Wall Street types or IP lawyers seeking to understand recurring patterns of problems and solutions in technology. Yep! If you are prepping hard for software engineering interviews

Nope! This course is not right for you if you are looking for a Programming 101 course. That’s not because there are pre-requisites, but simply because a Programming 101 course focuses on syntax, and on doing, while this course focuses on design, and on thinking.

Full details

Reviews:

“While it is repetitious at times, a highly thought through and very well presented course.” (Phani)

“The detailed explanations were extremely helpful to get a grip on the patterns. Especially nice was that patterns were compared and put into the context of other patterns where appropriate, and that a limited set of examples were used under different perspectives. However, in the first place I had expected to see more concrete instructions how to implement the patterns from scratch. Nevertheless, the course was really cool, thnx :)” (Markus Lommer)

“One of the best Udemy course I’ve taken! The instructors are extremely knowledgeable, they understand that design patterns are not inherently trivial at first glance, and make the effort to break things down in a way that is easily accessible.” (Maurice McFarlane)

  About Instructor:

Loony Corn

Loonycorn is us, Janani Ravi, Vitthal Srinivasan, Swetha Kolalapudi and Navdeep Singh. Between the four of us, we have studied at Stanford, IIM Ahmedabad, the IITs and have spent years (decades, actually) working in tech, in the Bay Area, New York, Singapore and Bangalore. Janani: 7 years at Google (New York, Singapore); Studied at Stanford; also worked at Flipkart and Microsoft Vitthal: Also Google (Singapore) and studied at Stanford; Flipkart, Credit Suisse and INSEAD too Swetha: Early Flipkart employee, IIM Ahmedabad and IIT Madras alum Navdeep: longtime Flipkart employee too, and IIT Guwahati alum We think we might have hit upon a neat way of teaching complicated tech courses in a funny, practical, engaging way, which is why we are so excited to be here on Udemy! We hope you will try our offerings, and think you’ll like them

Instructor Other Courses:

Learn by Example: JUnit Loony Corn, A 4-person team;ex-Google; Stanford, IIM Ahmedabad, IIT (0) $10 $20 Under the Hood: How Cars Work 25 Famous Experiments …………………………………………………………… Loony Corn coupons Development course coupon Udemy Development course coupon Software Engineering course coupon Udemy Software Engineering course coupon From 0 to 1: Design Patterns – 24 That Matter – In Java From 0 to 1: Design Patterns – 24 That Matter – In Java course coupon From 0 to 1: Design Patterns – 24 That Matter – In Java coupon coupons

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[rafi1228]

Discover the modern implementation of design patterns with C# and .NET

What you’ll learn

Recognize and apply design patterns

Refactor existing designs to use design patterns

Reason about applicability and usability of design patterns

Requirements

Good understanding of C#

Familiarity with latest C# features

Good understanding of object-oriented design principles

Description

Course Overview

This course provides a comprehensive overview of Design Patterns in C# and .NET from a practical perspective. This course in particular covers patterns with the use of:

The latest versions of C# and the .NET framework

Use of modern programming approaches: dependency injection, reactive programming and more

Use of modern developer tools such as ReSharper

Discussions of pattern variations and alternative approaches

This course provides an overview of all the Gang of Four (GoF) design patterns as outlined in their seminal book, together with modern-day variations, adjustments, discussions of intrinsic use of patterns in the language.

What are Design Patterns?

Design Patterns are reusable solutions to common programming problems. They were popularized with the 1994 book Design Patterns: Elements of Reusable Object-Oriented Software by Erich Gamma, John Vlissides, Ralph Johnson and Richard Helm (who are commonly known as a Gang of Four, hence the GoF acronym).

The original book was written using C++ and Smalltalk as examples, but since then, design patterns have been adapted to every programming language imaginable: C#, Java, PHP and even programming languages that aren’t strictly object-oriented, such as JavaScript.

The appeal of design patterns is immortal: we see them in libraries, some of them are intrinsic in programming languages, and you probably use them on a daily basis even if you don’t realize they are there.

What Patterns Does This Course Cover?

This course covers all the GoF design patterns. In fact, here’s the full list of what is covered:

SOLID Design Principles: Single Responsibility Principle, Open-Closed Principle, Liskov Substitution Principle, Interface Segregation Principle and Dependency Inversion Principle

Creational Design Patterns: Builder, Factories (Factory Method and Abstract Factory), Prototype and Singleton

Structrural Design Patterns: Adapter, Bridge, Composite, Decorator, Façade, Flyweight and Proxy

Behavioral Design Patterns: Chain of Responsibility, Command, Interpreter, Iterator, Mediator, Memento, Null Object, Observer, State, Strategy, Template Method and Visitor

Who Is the Course For?

This course is for .NET/C# developers who want to see not just textbook examples of design patterns, but also the different variations and tricks that can be applied to implement design patterns in a modern way. For example, the introduction of the DLR allows us to use an ImpromptuObject, so that our DynamicObject exposes any interface we desire. This allows for dynamic programming, and many design patterns are presented in terms of their static and DLR-based variations.

Presentation Style

This course is presented as a (very large) series of live demonstrations being done in Microsoft Visual Studio. Most demos are single-file, so you can download the file attached to the lesson and run it in Visual Studio, Visual Studio Code, Rider or another IDE of your choice.

This course does not use UML class diagrams; all of demos are live coding. I use Visual Studio, various NuGet packages, R# unit test runner and even dotMemoryUnit.

Who this course is for:

Beginner and experienced developers

Anyone interested in design patterns

Created by Dmitri Nesteruk Last updated 3/2019 English English [Auto-generated]

Size: 1.94 GB

   Download Now

https://ift.tt/2DCD4R2.

The post Design Patterns in C# and .NET appeared first on Free Course Lab.

[weiran99-blog]

Reflection on 11/19 discussion

In the reading, the author Jeff Friesen introduces design pattern, including what is the design pattern and the classification of design patterns. A design pattern describes the classes and interacting objects used to solve a general design problem in a specific context. Compare to software architecture, it’s more like an implementation. It’s easy to update and solves specific problems by using design patterns. Design pattern has advantage that it is reusable, extendable, manageable. However, it also has disadvantage that it’s difficult to read the code, and might be restrict. There are many common design patterns used, for example, composite, bridge, command, mediator. In our group, we discussed Flyweight and abstract factory. Flyweight takes similar data over and over again. For objects share an intrinsic characteristic, people only write the code once. If they want to create a specific object later, they can just modify the data instead of rewriting the code. How people choose a design pattern is an important question as well. They can first understand each of possible patterns and see which one fits in the code. Multiple design pattern can work together. If people found that old design pattern cannot fix the question, they will combine some characteristic from the old ones and create a new design pattern. In software engineering, double dispatch is an extension of single dispatch, when there are two objects interacting with each other. Double dispatch is often confused with method overloading. Java doesn’t support double dispatch.

[codeonedigest]

What is Flyweight design pattern? | Complete Tutorial with Java Examples

Hello friends, a new #video on #flyweight #design #pattern with #Java #example is published on #codeonedigest #youtube channel. Ultimate guide to flyweight #java design pattern. #flyweightdesignpattern #javadesignpatterns #flyweightdesignpatterninjava

What is Flyweight Design Pattern? Flyweight pattern provides a mechanism by which you can avoid creating a large number of ‘expensive’ objects and instead reuse existing instances to represent new ones. Flyweight pattern is useful in optimising the creation of too many objects by reusing the common data. Flyweight pattern reduce the creation of objects by sharing data, decrease memory footprint…

[tutorialspointexamples]

Java sql

Provides the API for accessing and processing data stored in a data source (usually a relational database) using the JavaTM programming language. This API includes a framework whereby different drivers can be installed dynamically to access different data sources. Although the JDBCTM API is mainly geared to passing SQL statements to a database, it provides for reading and writing data from any data source with a tabular format. The reader/writer facility, available through the javax.sql.RowSet group of interfaces, can be customized to use and update data from a spread sheet, flat file, or any other tabular data source. What are various DCL commands in SQL? Can you sort a column using a column alias? Is a null value same as zero or a blank space if not then what is the difference? How can you eliminate duplicate rows from a query result? Difference between TRUNCATE, DELETE and DROP commands? What is the difference between CHAR and VARCHAR2 datatype in SQL? What are the differences between sql and pl/sql? What are the transaction properties in sql? What is the sql case statement used for? How many types of aggregate functions are there in sql? What are scalar functions in sql? What is the difference between sql and mysql? What is the use of nvl function in sql? What do you mean by subquery? What are Indexes in SQL? How to create index in oracle sql? How to view index in oracle sql? How to get list of tables in oracle sql Difference between clustered and nonclustered indexes in oracle sql? How to update with select subquery in sql server Explain different types of index in sql server What is JavaScript? What are the advantages of JavaScript? What are the disadvantages of JavaScript? Is JavaScript a case-sensitive language? How to use external JavaScript file? How to create javascript object? How to add method to javascript object? What does the isNaN() function? What is the difference between undefined value and null value? How to access cookie using JavaScript? How to create cookie using JavaScript? How to read cookie using JavaScript? How to get cookie by name in JavaScript? How to delete cookie using JavaScript? How to redirect a url using JavaScript How to print a web page using JavaScript? How to handle exceptions in JavaScript? How to create a procedure? How to execute stored procedure? How to drop stored procedure? How to create a function? How to execute a function? How to drop a function? What is Context area? How to use explicit cursor? How to declare a cursor? How to fetch a cursor? How to close a cursor? Maven Eclipse Servlet Maven Eclipse JSP Maven Eclipse Spring Maven Eclipse Hibernate Maven interview questions What are the build tools in java? What are the aspects Maven manages? how to check the maven version in windows? how to check the maven version in linux? how to check the maven version in mac? What information does pom contain? What is a goal in maven? What are the types of repository in maven? Explain Maven repository search order What is local repository in maven? What is central repository in maven? What is remote repository in maven? What is maven plugin used for? What are the types of maven plugins? What is archetype in maven? How profiles are specified in maven? How can you build your project offline? How to exclude dependency in maven? Java cloning deep and shallow Shallow vs Clone copy Write a java program to find duplicate elements in an array? Write a java program to find second largest element in an array of integers? Write a java program to check the equality of two arrays? Write a java program to find all pairs of elements in an integer array whose sum is equal to a given number? Write a java program to find continuous sub array whose sum is equal to a given number? Write a java program to find the intersection of two arrays? Write a java program to separate zeros from non-zeros in an integer array? Write a java program to find all the leaders in an integer array? Write a java program to find a missing number in an integer array? Write a java program to convert an array to ArrayList and an ArrayList to array? Write a java program to count occurrences of each element in an array? Write a java program to reverse an array without using an additional array? Write a java program to remove duplicate elements from an array? Write a java program to find union and intersection of multiple arrays? Write a java program to find the most frequent element in an array? Java interview programs Java array interview questions Java array interview programs Java star pattern programs Java number pattern programs Spring security tutorial with examples Spring security overview Spring security architecture diagram Spring security maven dependency Spring security hello world xml example Spring security hello world annotation example Spring security custom login xml example Spring security custom login annotation example Spring security form login using database example Spring security limit login attempts example Spring security remember me example Spring security password encoder example Spring security hibernate xml example Spring security hibernate annotation example Spring boot tutorial with examples Spring boot overview Spring boot architecture diagram Spring boot components Spring boot starter parent in pom maven repo Spring boot web app configuration Run spring boot application from command line Spring boot hello world example Spring boot jsp example Spring boot restful web services example Spring boot common application properties Spring boot change default tomcat port Spring boot change context path Spring boot configuration properties example Spring boot slf4j example Spring boot ajax example Spring boot with mysql database example Spring boot with hibernate example How to log sql statements in spring boot? Spring boot deploy war file to tomcat Java design patterns tutorial with examples Java creational design patterns Java singleton design pattern Java factory design pattern Java abstract factory design pattern Java builder design pattern Java prototype design pattern Java structural design patterns Java adapter design pattern Java composite design pattern Java proxy design pattern Java flyweight design pattern Java facade design pattern Java bridge design pattern Java decorator design pattern Java behavioral design patterns Java template design pattern Java mediator design pattern Java chain of responsibility design pattern Java observer design pattern Java strategy design pattern Java command design pattern Java state design pattern Java visitor design pattern Java interpreter design pattern Java iterator design pattern Java memento design pattern How to iterate through collection objects? How to remove element from collection using iterator? Java Vector class How to read all elements in vector by using iterator in java? How to copy or clone a vector in java? How to add all elements of a list to vector in java? How to remove all elements from vector in java? How to copy vector to array in java? How to get sub list from vector in java? how to display arraylist values by using iterator in java? How to copy or clone a arraylist in java? How to add all elements of a list to arraylist in java? How to remove all elements from arraylist in java? How to convert arraylist to array in java?

[mlbors]

The Flyweight Pattern

In this article we are going to take a look at the Flyweight Pattern to understand how it works and how we can use it.

Introduction

The Flyweight Pattern is a Structural Pattern. Its intent is to minimize memory usage. The famous Gang of Four defines it like so:

"Use sharing to support large numbers of fine-grained objects efficiently. A Flyweight is a shared object that can be used in multiple contexts simultaneously. The flyweight acts as an independent object in each context; it’s indistinguishable from an instance of the object that’s not shared."

There is a lot of information in this definition. So, let's illustrate it with a "real world" example: imagine that we are building a video game where a thousand characters have to fight on the battlefield. Each character is an object that contains, for example, a graphical representation, a behaviour, weapons and information about its location and its health. Creating such a number of objects will use a lot of memory. We can improve that by sharing the common information, such as graphical representation and behaviour. Health and location will, however, vary.

Now we have that in mind, let's dig a little deeper.

The Pattern

The intent of the Flyweight Pattern is to use sharing to support a large number of objects that have part of their internal state in common while the other part of state varies.

A common practice is to keep state in external data structures and pass them to the Flyweight Object when needed. Each Flyweight Object is divided into two pieces: the state-dependent (extrinsic) part, and the state-independent (intrinsic) part.

The intrinsic data is held in the properties of the Flyweight Objects that are shared. Intrinsic State is invariant, so it is context independent. In that sense, intrinsic properties make objects "constant". The extrinsic data is context dependent. So it cannot be shared and must be passed in through arguments, but should never be stored within a shared Flyweight Object. In our video game example, the graphical representation would be the intrinsic data and the location and the health would be the extrinsic data.

This pattern is useful when we have a program using a large number of objects. This pattern is often combined with Composite to implement shared leaf nodes.

Structure

To apply this pattern, we need the following things:

Flyweight

It declares an interface through which Flyweights can receive and act on extrinsic state.

Concrete Flyweight

It implements the Flyweight interface and adds storage for intrinsic state

Unshared Concrete Flyweight

It provides a way to use this pattern without enforcing the shared concept.

Flyweight Factory

It creates and manages Flyweight objects and ensures that Flyweights are shared properly. It keeps track of the Flyweights that already exist and when it is asked to create a new Flyweight, it checks if a matching Flyweight already exists. If there is no object of the required type, it creates a Flyweight of the requested type, adds it to the pool, and returns a reference to the Flyweight.

Client

It maintains a reference to Flyweights, computes or stores the extrinsic state of those.

Example

Let's take back our example with our video game and let's make a really basic implementation of this pattern with Java.

First, we define the Flyweight interface:

public interface Character { public void render(); }

We can now create a concrete implementation:

public class CharacterA implements Character { private String color; private int x; private int y; public Circle(String color){ this.color = color; } public void setX(int x) { this.x = x; } public void setY(int y) { this.y = y; } public void render() { System.out.println("Character at position " + x + ", " + y + " with color " + color); } }

Let's make the Factory that embeds a Pool system:

public class CharacterFactory { private static HashMap<String, Character> characterMap = new HashMap(); public static Character getCharacter(String color) { Character character = (Character)characterMap.get(color); if (character == null) { character = new CharacterA(color); characterMap.put(color, character); } return character; } }

And we can make our Client like so:

public class CharacterClient { private static final String colors[] = { "Red", "Green", "Blue", "White", "Black" }; public static void main(String[] args) { for (int i = 0; i < 15; ++i) { Character character = (Character)CharacterFactory.getCharacter(getRandomColor()); character.setX(getRandomX()); character.setY(getRandomY()); character.render(); } } private static String getRandomColor() { return colors[(int)(Math.random() * colors.length)]; } private static int getRandomX() { return (int)(Math.random() * 100); } private static int getRandomY() { return (int)(Math.random() * 100); } }

Conclusion

In this article, we saw what the Flyweight Pattern is and how it works. This pattern is used to minimize memory usage by sharing as much as possible with similar objects. We saw that it is based on the following things: Flyweight, Concrete Flyweight, Unshared Concrete Flyweight, Flyweight Factory and Client.

One last word

If you like this article, you can consider supporting and helping me on Patreon! It would be awesome! Otherwise, you can find my other posts on Medium and Tumblr. You will also know more about myself on my personal website. Until next time, happy headache!

[javatutorialcorner]

Design Patterns - Strategy Pattern

Strategy Pattern

Definition

Use strategy when you need to define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it. Related patterns include State, Flyweight, Decorator, Composite.

Where to use

•When you need to use one of several algorithms dynamically. •When you want to configure a class with one of many related classes (behaviors). •When an algorithm uses data that clients shouldn't know about.

Benefits

•Reduces multiple conditional statements in a client. •Hides complex, algorithmic-specific data from the client. •Provides an alternative to subclassing. •Can be used to hide data that an algorithm uses that clients shouldn't know about.

Drawbacks/consequences

•Clients must be aware of different strategies. A client must understand how strategies differ before it can select the appropriate one. •Increases the number of objects in an application.

Strategy Pattern Class Diagram

In the class-diagram above: •The Strategy interface defines the behavior that is common to all the concrete implementations. •The ConcreteStrategy encapsulates an implementation of a specific algorithm or behavior that is defined through the Strategy interface. •The Context provides certain services that is defined by the Strategy interface and implemented by different ConcreteStrategy classes depending on behavior.

Strategy Pattern Example

This example uses sorting algorithms. Two sorting algorithms (Bubble sort and Quick sort) are implemented and the client can select either of the algorithms. The SortInterface describes what the algorithms must be able to do, sort(). The classes QuickSort and BubbleSort both implements the SortInterface and each have their own algorithm for sorting. SortingContext maintains a reference to a Strategy object and forwards client requests to the strategy. SortingClient set the concrete strategy in the context and invokes the context to run the algorithm.

public interface SortInterface { public void sort(double[] list); } public class QuickSort implements SortInterface { public void sort(double[] u) { sort(u, 0, u.length - 1); } private void sort(double[] a, int left, int right) { if (right <= left) return; int i = part(a, left, right); sort(a, left, i-1); sort(a, i+1, right); } private int part(double[] a, int left, int right) { int i = left; int j = right; while (true) { while (a[i]< a[right]) i++; while (smaller(a[right], a[--j])) if (j == left) break; if (i >= j) break; swap(a, i, j); } swap(a, i, right); return i; } private boolean smaller(double x, double y) { return (x < y); } private void swap(double[] a, int i, int j) { double swap = a[i]; a[i] = a[j]; a[j] = swap; } } public class BubbleSort implements SortInterface { public void sort(double[] list) { //Bubblesort algorithm here } } public class SortingContext { private SortInterface sorter = null; public void sortDouble(double[] list) { sorter.sort(list); } public SortInterface getSorter() { return sorter; } public void setSorter(SortInterface sorter) { this.sorter = sorter; } } public class SortingClient { public static void main(String[] args) { double[] list = {1,2.4,7.9,3.2,1.2,0.2,10.2, 22.5,19.6,14,12,16,17}; SortingContext context = new SortingContext(); context.setSorter(new QuickSort()); context.sortDouble(list); for(int i =0; i< list.length; i++) { System.out.println(list[i]); } } }

When SortingClient is executed the result is:

c:>0.2 c:>1.0 c:>1.2 c:>2.4 c:>3.2 c:>7.9 c:>10.2 c:>12.0 c:>14.0 c:>16.0 c:>17.0 c:>19.6 c:>22.5

Strategy Pattern Usage Example

The strategy pattern is used in the implementation of the LayoutManager in Java. The LayoutManager can be configured to work with different layout objects, such as FlowLayout, CardLayout, GridLayout, etc. These classes encapsulate the actual algorithms for laying out visual components that the LayoutManager uses to render the interface on the screen. By changing the Layout (algorithm) we can dynamically change how the interface is rendered.

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