Design-Patterns | : key : Gof Design Patterns Implementation | Architecture library

 by   CyC2018 Java Version: Current License: No License

kandi X-RAY | Design-Patterns Summary

kandi X-RAY | Design-Patterns Summary

Design-Patterns is a Java library typically used in Architecture applications. Design-Patterns has no bugs, it has no vulnerabilities and it has low support. However Design-Patterns build file is not available. You can download it from GitHub.

代码基于《Head First 设计模式》与《设计模式: 可复用面向对象软件的基础》,尽量保证简单易懂。.

            kandi-support Support

              Design-Patterns has a low active ecosystem.
              It has 200 star(s) with 97 fork(s). There are 13 watchers for this library.
              It had no major release in the last 6 months.
              There are 1 open issues and 1 have been closed. There are no pull requests.
              It has a neutral sentiment in the developer community.
              The latest version of Design-Patterns is current.

            kandi-Quality Quality

              Design-Patterns has no bugs reported.

            kandi-Security Security

              Design-Patterns has no vulnerabilities reported, and its dependent libraries have no vulnerabilities reported.

            kandi-License License

              Design-Patterns does not have a standard license declared.
              Check the repository for any license declaration and review the terms closely.
              Without a license, all rights are reserved, and you cannot use the library in your applications.

            kandi-Reuse Reuse

              Design-Patterns releases are not available. You will need to build from source code and install.
              Design-Patterns has no build file. You will be need to create the build yourself to build the component from source.

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            Design-Patterns Key Features

            No Key Features are available at this moment for Design-Patterns.

            Design-Patterns Examples and Code Snippets

            Javadot img1Lines of Code : 74dot img1no licencesLicense : No License
            copy iconCopy
            public abstract class StealingMethod {
              protected abstract String pickTarget();
              protected abstract void confuseTarget(String target);
              protected abstract void stealTheItem(String target);
              public void steal() {
                var target = pickTa  

            Community Discussions


            Getting mapper_parsing_exception in OpenSearch
            Asked 2022-Mar-30 at 03:46

            I'm new to OpenSearch, and I'm following the indexing pattern mentioned here for a POC.

            I'm trying to test the mapping mentioned here : in OpenSearch dev console.



            Answered 2022-Mar-30 at 03:46

            You need to replace page by _doc (or remove it altogether) as there's no more mapping types



            Visitor Pattern and Double Dispatch
            Asked 2022-Feb-23 at 19:13

            I know this is well trodden territory but I have a specific question... I promise.

            Having spent very little time in the statically typed, object oriented world, I recently came across this design pattern while reading Crafting Interpreters. While I understand this pattern allows for extensible behavior (methods) on a set of well defined existing types (classes), I don't quite get the characterization of it as a solution to the double dispatch problem, at least not without some additional assumptions. I see it more as making a tradeoff to the expression problem, where you trade closed types for open methods.

            In most of the examples I've seen, you end up with something like this (shamelessly stolen from the awesome Clojure Design Patterns)



            Answered 2022-Feb-23 at 19:13

            The comment from @user207421 is spot on. If a language does not natively support double dispatch, no design pattern can alter the language to make it so. A pattern merely provides an alternative which may solve some of the problems that double dispatch would be applied to in another language.

            People learning the Visitor Pattern who already have an understanding of double dispatch may be assisted by explanations such as, "Visitor solves a similar set of problems to those solved by double dispatch". Unfortunately, that explanation is often reduced to, "Visitor implements double dispatch" which is not true.

            The fact you've recognized this means you have a solid understanding of both concepts already.



            What does composition mean in the composition vs inheritance debate?
            Asked 2022-Feb-04 at 23:54

            I was learning about the Bridge Design pattern. To quote:

            The Bridge pattern attempts to solve this problem by switching from inheritance to the object composition. …

            And then, the following image is shown:

            When people are talking about composition as an alternative for inheritance, do they refer to both aggregation and composition relationships? If not, what do they mean exactly?

            I wonder this because the picture has an aggregation relationship between Color and Shape, not a composition one.



            Answered 2022-Feb-03 at 13:37

            Normally, when people talk about using composition vs. inheritance, they are talking about alternative ways of solving the same problem. In both cases, a "base class" provides an implementation of an interface that you want to reuse in your "derived class"

            When you implement this with inheritance, there is an undesirable is-a relationship between the derived class and the base class, with the effect that implementation details of the base class, which should be hidden, can become changes in the derived class class.

            When you implement this with composition -- a real composition relationship -- the "derived" only has an is-a relationship with the interface that it wants to implement, and the cost of this is that it must delegate calls to the "base" class.

            In the Bridge pattern, which you reference, the goal is a little different. You do want to isolate the containing class from change to the connected implementation, but there is no is-a relationship between the containing class and an interface of the contained class.

            The relationship between them may be one of composition, or may be simple aggregation -- that is an implementation detail. Often, the concrete implementation of the contained class will be injected as an interface into the containing class constructor, and in that case the relationship is just aggregation.



            Is there any way to make the method return a mutable value?
            Asked 2022-Feb-01 at 00:20

            as shown in the code below:



            Answered 2022-Jan-28 at 02:13

            You're using the wrong dynamic method. What you want is dynamicMemberLookup. Watch closely. First, the preparation:



            How can I get the current move from the score director?
            Asked 2021-Nov-29 at 09:25

            We are using the "auto delay until last" pattern from the docs,

            The loop detection computation is extremely expensive, and we would like to minimize the number of times it is called. Right now, it is being called in the @AfterVariableChanged method of the arrival time shadow variable listener.

            The only information I have available in that method is the stop that got a new previous stop and the score director. A move may change several planning variables, so I will be doing the loop detection once for every planning variable that changed, when I should only have to do it once per move (and possibly undo move, unless I can be really clever and cache the loop detection result across moves).

            Is there a way for me, from the score director, to figure out what move is being executed right now? I have no need to know exactly what move or what kind of move is being performed, only whether I am still in the same move as before.

            I tried using scoreDirector.toString(), which has an incrementing number in it, but that number appears to be the same for a move and the corresponding undo move.



            Answered 2021-Nov-29 at 09:25

            No, there is no access to a move from scoring code. That is by design - scoring needs to be independent of moves executed. Any solution has a score, and if two solutions represent the same state of the problem, their scores must equal - therefore the only thing that matters for the purposes of scoring is the state of the solution, not the state of the solver or any other external factor.



            Should I use the "delete" for the object member which initialized by "new" operator in constructor?
            Asked 2021-Oct-20 at 07:00

            I have a question about new and delete: Should I use delete for the input parameter or member object, e.g.:


            Should I use delete on the object allocated by new FlyNewWay()?



            Answered 2021-Oct-20 at 07:00

            Yes whenever you use new keyword to allocate some memory then you must always use delete to free up that memory later when no longer needed. Otherwise you will have a memory leak as in your program. In your case you should use delete inside the destructor in the MallarDuck.cpp .

            Other solution would be to use smart pointers like unique_ptr so that you don't have to explicitly free the memory.

            unique_ptr`'s syntax would something like:



            Why are there different ways to describe same design pattern using UML? What to trust?
            Asked 2021-Aug-31 at 08:47

            I find it difficult to learn both Design Pattern and UML since there are different ways to describe the same pattern which make me unsure what is the single source of truth.

            Take Iterator pattern for example, here are just a few diagrams that I saw from well-known sites:

            1 WIKIPEDIA


            2 TUTORIALS POINT


            3 REFACTORING GURU


            4 OODESIGN


            5 HOWTODOINJAVA


            What confuses me the most is how arrow symbols are used to describe the relationship between these classes. Sometimes they are generalization, sometimes interface realization, directed association or dependency. Even composition is also used...

            I wonder what would be the best way for me to get my head around all this.



            Answered 2021-Aug-31 at 08:47

            In general, one needs to be very careful when looking at UML models for design patterns. There are three reasons:

            • The reference for design patterns is the GoF. This book was published in 1995, before UML even existed, and used a variation of the OMT notation (an ancestor of UML). In case if doubts, this is the source to trust.
            • The Java language design was made public in 1995, JDK 1.0 release in January 1996, and the language not yet widely known. The authors based their designs and code examples on a C++ class model, i.e. on classes and inheritance only, without bothering for multiple inheritance. Most modern languages do not support multiple inheritance. As a consequence, some of the original patterns have to be adapted for Java, C# or Swift, to make a distinction between classes, abstract classes and interfaces, and between inheritance and interface implementation. There are multiple ways to do this. For example, some systematically converted abstract classes to interfaces. Some converted them only when there was a conflict. And some converted according to the interface "spirit".
            • Misunderstandings happen. Some people publish such diagrams on the net but misunderstand the pattern, or misunderstand UML, or both together. Also, Gamma et al started the book when they were PhD students and also made some mistakes. You'll find for example some inconcsitencies in their use of the OMT aggregation.
            • The worst case is the Builder pattern, where you have not only those problems, but on top of that you have a naming conflict: a very popular Java book introduced a (very different) variant of the builder pattern, with a different intent and another design, which caused total confusion.

            Now to your specific example, and based on the content you have provided:

            • oodesign is the closest to the original pattern and fully accurate. Btw, I mostly use links to their pages when it comes to patterns.
            • refactoring guru is also a good choice. They opted to use interfaces instead of abstract classes, which is fine. But they have redefined the interface's operations and properties (probably in relation to own examples) and require a bidirectional navigation that seems not justified. If you're interested, there is a "Head First: Design patterns" which uses a similar mapping but keeps the original interface.
            • wikipedia is not bad either: they have left out the client (which the GoF showed in light gray, to suggest that it's not essential for this pattern); They are more precise and complete on dependencies; But they also redefined the operations and properties differently. And they added an unnecessary aggregation symbol.
            • How to make it in Java is confusing, because they kept one abstract class and opted for an interface for the other. And they have hidden the operations and properties. But there's nothing fundamentally wrong at first sight.
            • Forget about tutorial points, at least for this UML diagram. It's plain wrong, as @qwerty_so already mentioned in the comments.

            The statement of accuracy is for this pattern only and for the current version of the content. This cannot be generalized to all the design patterns in view of my introductory remarks.



            Implement "Chain of Responsibility" pattern with async functions
            Asked 2021-Aug-11 at 19:40

            I need to run multiple async operations, until one of them returns a certain result - in other words, the "Chain of Responsibility" pattern.

            When I tried to implement it, some was the first thing that came up. However I'm having troubles with the asynchronous calls, as the loop gets "stuck" after the first iteration:



            Answered 2021-Aug-11 at 19:40


            How should a "Bridge" design pattern be implemented for more than two hierarchies?
            Asked 2021-Jun-10 at 00:51

            This explains the "Bridge" pattern I'm referring to:

            Here's a scenario from the post above:

            Say you have a geometric Shape class with a pair of subclasses: Circle and Square. You want to extend this class hierarchy to incorporate colors, so you plan to create Red and Blue shape subclasses. However, since you already have two subclasses, you’ll need to create four class combinations such as BlueCircle and RedSquare.

            The problem this scenario presents:

            Adding new shape types and colors to the hierarchy will grow it exponentially. For example, to add a triangle shape you’d need to introduce two subclasses, one for each color. And after that, adding a new color would require creating three subclasses, one for each shape type. The further we go, the worse it becomes.

            To avoid this problem, we implement the Bridge pattern like so:

            Extract the color-related code into its own class with two subclasses: Red and Blue. The Shape class then gets a reference field pointing to one of the color objects. Now the shape can delegate any color-related work to the linked color object. That reference will act as a bridge between the Shape and Color classes. From now on, adding new colors won’t require changing the shape hierarchy, and vice versa.

            I understand the how and why of this implementation.

            But what if we need a third hierarchy, e.g. BorderStyle (where a border style can be Straight, Wavy, or ZigZag?)

            I guess we could implement a second Implementor class for BorderStyle and pass it into a Shape constructor like so:



            Answered 2021-Jun-10 at 00:45

            Yes, this works. There's nothing wrong with adding two Bridge relationships to one abstraction (beyond the complexity of juggling three different hierarchies).

            Decorator would certainly not work for this purpose, because it maintains a single hierarchy, which is known to the client. The Implementor hierarchy in a Bridge (or hierarchies in this case) are unknown to the client.

            I would make a clarification to the linked article, where it says,

            You want to extend this [shape] class hierarchy to incorporate colors

            I think this oversimplifies the motivation for a Bridge. The Implementors are not just some attributes you choose to add to your Abstraction to enhance it. Your Abstraction requires an Implementor in order to function at all. The method implementations within subclasses of Abstraction generally do little except call methods of the Implementor.

            The Abstraction represents your high-level, business API, while the Implementor represents a lower-level, primitive API. They are both abstractions, but at different levels. I don't think this is conveyed adequately by shape & color examples because shape and color seem like abstractions at the same level. Both shape and color would be known to the clients, and neither one strictly depends on the other.

            So a Bridge is applied for more specific reasons than the given example, but you certainly can have two.



            CMake with ROS Package:Header files not detected
            Asked 2021-Jun-09 at 04:22

            I am trying to organise my code into a more OOP style with each class taking on its own header and cpp file. This is my tree in the package folder in the workspace



            Answered 2021-Jun-09 at 02:37

            In essence you don't need to include either header into the other. This fixes the circular includes. In ROS_Topic_Thread.h, friend class Master_Thread; already forward declares Mater_Thread, so you don't need the Master_Thread.h header. In Master_Thread.h, you can also forward declare class ROS_Topic_Thread; before the declaration of the Master_Thread class, since you only use references to ROS_Topic_Thread in the transfer_to_master_buffer method.


            Community Discussions, Code Snippets contain sources that include Stack Exchange Network


            No vulnerabilities reported

            Install Design-Patterns

            You can download it from GitHub.
            You can use Design-Patterns like any standard Java library. Please include the the jar files in your classpath. You can also use any IDE and you can run and debug the Design-Patterns component as you would do with any other Java program. Best practice is to use a build tool that supports dependency management such as Maven or Gradle. For Maven installation, please refer For Gradle installation, please refer .


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