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adadevacademy · 6 years ago

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Teaching Inheritance

by Dan Roberts, Lead Instructor

Not one of them is like another. Don't ask us why. Go ask your mother. -- Dr. Seuss

Think back to when you were learning your first object-oriented programming language. If you learned to program in the last 15 years, there's a good chance that was your first language, period. You probably started off with simple concepts like conditionals and loops, moved on to methods, and then to classes. And then at some point your instructor (or mentor or tutorial video) introduced a concept called inheritance.

If you're like me, your first exposure to inheritance was a bit of a mess. Maybe you couldn't quite get a handle on the syntax. Or maybe you were able to make it work on the class project and pass the exam, but couldn't quite figure out where you would ever use this in the real world. And then once that introductory course was over, you probably packed inheritance back up into your mental toolbox and didn't use it again for a long time.

The fact is, inheritance is complicated. It's hard to use correctly, even for experienced engineers - it took me several years in industry before I felt like I had a good handle on the subject. Yet inheritance is a tool with first-class support in most modern languages, and which is taught to many novice programmers almost immediately.

In this blog post I'll dive into why teaching inheritance is hard, some of the problems with current methods, and what Ada Developers Academy is doing to try and address this problem.

Do We Need Inheritance?

The first question we should ask is, "do we really need to teach inheritance?" This might seem like a silly question - everyone teaches inheritance, it's a key part of object-oriented programming! However time is a scarce resource in a program like Ada's, and everything we do teach means there's something else we don't teach. We've found more often than you might expect that we can drop something that "everyone" does, and end up with a leaner curriculum that is more valuable to both our students and their employers.

But as it turns out, we do need to teach inheritance. This is due to the way we leverage frameworks like Ruby on Rails and ReactJS later in the course. Both Rails and React use inheritance at a fundamental level, and our curriculum wouldn't make sense without it. Moreover, inheritance is an important technique for building real-world software, and our graduates use it on a regular basis in the wild.

Whether inheritance should be taught to novices who don't have an immediate need for it, for example in the first year of a 4-year university program in CS, is a different question. It's also not a problem I'm being paid to solve / write a blog post about. We know that the curriculum we cover at Ada does need inheritance, so we can confidently move forward with our analysis.

What it Means to Teach Inheritance

I have heard using inheritance when writing software compared to using a lathe as a craftsperson. Both solve a certain class of problem extremely well, and neither is particularly useful if you don't have that problem. Both lathes and inheritance take a fair bit of training to use well, and both are liable to make a big mess if used incorrectly. Every machine shop has a lathe, and most modern programming languages support inheritance.

The lathe metaphor allows us to break down the problem a little more. Thinking about it this way, we can see that any curriculum on inheritance needs to address two types of questions.

How do you use inheritance? What specific syntax do you need, and how does that change the way information flows through your program? What rules do you need to keep in mind as you work (e.g. Liskov substitution, the open-closed principle)? These questions are more mechanical, and the answers are often language-specific.

When should you use inheritance? How do you identify that a problem is likely to be neatly solved by inheritance, or that inheritance is a poor choice? What are the tradeoffs involved in deciding whether or not to use inheritance? These questions are more theoretical, and the answers are likely to apply no matter what language or framework you use.

Thinking about these questions leads us to two main issues that make teaching inheritance difficult:

The syntax and semantics of inheritance are tricky

Problems that are well-suited to inheritance are complex

Let's dive into each of these a little deeper.

Programming with Inheritance is Tricky

One of the main reasons teaching inheritance is hard is because inheritance itself is hard. At a high level inheritance is easy to explain: one class gets all the code from another class, and can override pieces and add its own bits. As so often happens, the devil is in the details.

For example, with Ruby the following questions arise:

Are static methods inherited? Can they be overridden?

How are instance variables, class variables, and class-instance variables handled?

Can constants be overridden? If not, what should you do instead?

How does inheritance interact with nested classes?

What has precedence, methods from the parent class or from a mixin?

And that's for Ruby, which is supposed to be beginner friendly! Other languages have their own wildcards:

Python: multiple inheritance

JavaScript: prototypical inheritance model, multiple types of functions

Java: static typing and explicit polymorphism, interfaces, templating

C++: all the Java problems plus memory management and object slicing (shudder)

Whatever language you choose, there's going to be a lot of rules to remember. How do you encode all these, especially for a novice? How do you decide what to include up-front, what to put in the appendix, what to omit entirely? How do you introduce specific details while still keeping the discussion general enough to translate to other languages? This is an important part of the problem - all your theoretical knowledge of how inheritance is used and what kinds of problems it solves won't do you any good if you can't apply it in code.

Fortunately, this part of the problem of teaching inheritance is well-understood. There are many excellent texts that round up the complicated syntax and semantics of inheritance into digestible, intuitive chunks. Any alternative treatment of inheritance needs to acknowledge this challenge and build upon this existing work.

Problems that Need Inheritance are Complex

The other reason that teaching inheritance is hard is because problems that benefit from inheritance tend to be complex. At a minimum, a problem to be solved with inheritance needs:

Two or more domain objects that are similar enough they need to share code, but not so similar that they could be combined into one class

Enough other things going on that it's worth encapsulating the domain objects as classes in the first place

That's a non-trivial amount of complexity, especially for a classroom full of beginners. How can you reasonably build a school project that establishes this complexity, but still fits within the tight time limits of the course? This is where existing curriculums tend to break down.

One tool that springs to mind to address this challenge is scaffolding, possibly by implementing some portion of a project in advance. This allows an instructor to reduce the complexity of the work required of the student, without reducing the complexity of the problem space as a whole. Deciding exactly what and how much to scaffold requires us to do a little more research, so we'll come back to this problem later.

How is Inheritance Used?

Since Ada is a workforce development program, one of the most valuable things we can do is ask "what's going on in industry?" Specifically,

How is inheritance used in the real world?

How is inheritance most likely to be used by a junior engineer in their first year or so on the job?

Understanding how inheritance is used can give us some direction on how it should be taught. Let's look at a few examples.

Rails

In Rails, almost every class you write will inherit from something. The two most common are

ActiveRecord::Base for models

ActionController::Base for controllers

You also see inheritance used for everything from database migrations to configuration management - its the Rails Way™. If you want to do something, you inherit from a class somewhere in the Rails framework. These superclasses are generally quite abstract, and each covers some functionality specific to the domain of an MVC framework.

Another important idiom is the template method pattern, as made famous in the Gang of Four book. A great example of this is with database migrations, where you define an class that inherits from ActiveRecord::Migration and implement the change method, and Rails takes care of the rest. Controller actions also mimic the template method pattern, particularly if your application uses the builtin tools for RESTful routing.

For the most part, Rails does not have you define your own superclasses. The exception to this is ApplicationRecord and ApplicationController, which sit in the hierarchy between concrete models or controllers and the abstract Rails implementation - these are generated automatically by Rails, but are open for you to modify.

React

React isn't quite as broad in its use of inheritance as Rails. However, every component class inherits from React.Component.

In React we again see the template method pattern pop up. Whether you're implementing render or componentDidMount, React knows the algorithm and you fill in the details.

React also does not encourage defining your own superclasses. In fact, their official documentation is rather explicit that inheritance between components should be avoided.

Other Frameworks

Rails and React are the two industry-grade frameworks I'm most familiar with, but I've dabbled in some others, namely Android (Java) and Unity (C#).

Android follows a similar pattern: everything you write inherits from some builtin class, template methods abound, and developers are discouraged from building their own inheritance relationships.

Unity matches the pattern as well, but they seem to be more lenient about extending your own classes, at least as far as I can tell from the Unity documentation on inheritance.

Industry Experience

This matches my experience of how engineering work tends to be done. Design work, in this case identifying the abstraction and building the superclass, is done by the team as a whole or by someone with an impressive sounding job title like "principal consulting systems architect". Implementing the details in a subclass is the job of an individual engineer.

Concretely, as I was spinning up at Isilon I spent a lot of time working on C++ and Python classes that filled in the details of an existing pattern, and not a lot of time inventing new patterns. Template methods were something I used frequently without having a name for them, and which I later wished I had learned about in college.

Summary

Setting Use case Write subclasses Write superclasses Abstract classes Template methods Rails Web servers ✅ ❌ ✅ ✅ React Single-page applications ✅ ❌ ✅ ✅ Android Mobile apps ✅ ❌ ✅ ✅ Unity Video games ✅ ✅ ✅ ✅ First year in industry Any or none of the above ✅ ❓ ✅ ✅

There are a few clear takeaways from this quick survey:

Inheritance solves a complex problem. Programs that benefit from inheritance tend to be fairly large

Writing a subclass is much more common than writing a superclass

Often the superclass is provided for you by whatever framework you're using

Superclasses tend to be abstract, both semantically (embodying a high-level concept) and functionally (never instantiated)

The template method pattern is extremely important

Existing Work

We've built an understanding of what a new engineer needs from an introduction to inheritance. How well does existing computer science curriculum match up with this?

Building Java Programs

We'll use a case study to demonstrate: the excellent Building Java Programs: A Back to Basics Approach by Stuart Reges and Marty Stepp. This text is used by many introductory CS courses, including the University of Washington, as well as by AP CS classrooms supported by the TEALS program. My first exposure to the book was while teaching with TEALS back in 2014.

Building Java Programs does an great job introducing the vocabulary and syntax of inheritance.

The first example is different types of employees in an HR system. This is simple enough to demonstrate syntax while still somewhat plausible - not an easy balance to strike.

The text includes a discussion of where inheritance is not appropriate, and the difference between is-a and has-a relationships.

The chapter introduces interfaces, abstract classes and abstract methods, and the ability to override a method. However, it makes no mention of the template method pattern.

The chapter finishes with a more complex example dealing with different types of stocks and assets.

This is substantial enough that inheritance is an appropriate technique.

In this example, the pieces at the top of the hierarchy are abstract (an interface and an abstract class), matching the pattern identified above.

The book does not provide any context for how this code will be used. I would argue this is a major oversight. Writing code in a vacuum is fine for experienced engineers, but in my experience novices benefit from concrete examples of how code will be used from the "outside". With inheritance in particular, this would demonstrate how polymorphism is useful.

There is no mention of the idea of extending a class implemented by a framework.

In general Building Java Programs is excellent, and I have a tremendous amount of respect for Reges and Stepp. It certainly did a good job of preparing my students for the AP CS exam. However, it does not introduce inheritance as it is used in the real world, particularly by novice engineers. As far as I can tell this is typical of introductory CS courses - certainly my undergraduate education at Purdue followed a similar pattern.

Design Textbooks

There is another type of text that addresses inheritance: books on software design. Famous resources like Practical Object-Oriented Design: An Agile Primer Using Ruby (POODR) by Sandi Metz, or Design Patterns (the "Gang of Four" book) by Gamma, Helm, Johnson and Vlissides address software design more generally, employing inheritance as one tool among many.

However, these books are targeted at experienced engineers trying to up their game, not at novices learning their chosen language for the first time. Moreover they discuss design from a ground-up perspective, whereas an engineer beginning their career is likely to build on the shoulders of giants, extending existing designs rather than inventing new ones.

An ideal curriculum would bridge the gap between these two approaches, introducing both syntax and common inheritance idioms, and getting new engineers used to the work of extending an existing class.

Ada's Approach to Inheritance

The instructional team at Ada has been unhappy with our approach to inheritance for a while now, but we haven't quite known what to do about it. Now that we've done some research and formalized our engineering and pedagogical intuition, here's the approach we've come up with:

Simple examples and accessible metaphors are fine for introducing syntax and semantics, though as Reges and Stepp demonstrate they don't have to be completely unrealistic.

Common idioms like abstract classes and the template method pattern should be introduced as soon as the basic syntax is understood.

Students' first serious inheritance project should involve extending an existing superclass.

This matches the way inheritance is used in the real world, and makes the benefits (not having to re-write a bunch of code) immediately clear.

Instructors would provide the following scaffolding:

Superclass implementation

Driver code demonstrating polymorphism

Another subclass, to model the inheritance mechanism

Possibly a test suite or test stubs

If time permits, a second inheritance project would focus on design, and have students build both the superclass and subclasses, as well as driver code.

At Ada, the first inheritance project takes the form of OO Ride Share. Students are asked to load information about drivers, passengers and trips from CSV files; we provide a CsvRecord superclass and Passenger and Trip subclasses pre-built. We feel this problem is complex enough to justify inheritance but simple enough to spin up on quickly. It also mimics the way ActiveRecord is used in Rails, which will hopefully lead to more comfort and deeper understanding once we get into our Rails unit.

The second project is still in the planning phase, but the idea is a command-line app that integrates with the Slack API. After an in-class design activity students will implement a Recipient superclass that handles most of the API interaction, and User and Channel subclasses that fill in the details. They will also build a command loop that interacts with the user, demonstrating the power of polymorphism. We don't have the project write-up finished yet, but there is a prototype of the end product.

We've spent a lot of time thinking about this fresh approach to teaching inheritance, and I'm excited to see the results. Watch this space for an update in a couple months as we conclude our Intro to Ruby unit and move into Rails.

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prachivermablr · 5 years ago

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siva3155 · 5 years ago

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300+ TOP Elasticsearch Interview Questions and Answers

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vespaengine · 8 years ago

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The basics of Vespa applications

Distributed computation over large data sets in real-time — what we call big data serving — is a complex task. We have worked hard to hide this complexity to make it as easy as possible to create your own production quality Vespa application. The quick start guides take you through the steps of getting Vespa up and running, deploying a basic application, writing data and issuing some queries to it, but without room for explanation. Here, we'll explain the basics of creating your own Vespa application. The blog search and recommendation tutorial covers these topics in full detail with hands-on instructions.

Application packages

The configuration, components and models which makes out an application to be run by Vespa is contained in an application package. The application package:

Defines which clusters and services should run and how they should be configured

Contains the document types the application will use

Contains the ranking models to execute

Configures how data will be processed during feeding and indexing

Configures how queries will be pre- and post-processed

The three mandatory parts of the application specification are the search definition, the services specification, and the hosts specification — all of which have their own file in the application package. This is enough to set up a basic production ready Vespa applications, like, e.g., the basic-search sample application. Most applications however, are much larger and may contain machine-learned ranking models and application specific Java components which perform various application specific tasks such as query enrichment and post-search processing.

The search definition

Data stored in Vespa is represented as a set of documents of a type defined in the application package. An application can have multiple document types. Each search definition describes one such document type: it lists the name and data type of each field found in the document, and configures the behaviour of these. Examples are like whether field values are in-memory or can be stored on disk, and whether they should be indexed or not. It can also contain ranking profiles, which are used to select the most relevant documents among the set of matches for a given query - and it specifies which fields to return.

The services definition

A Vespa application consists of a set of services, such as stateless query and document processing containers and stateful content clusters. Which services to run, where to run those services and the configuration of those services are all set up in services.xml. This includes the search endpoint(s), the document feeding API, the content cluster, and how documents are stored and searched.

The hosts definition

The deployment specification hosts.xml contains a list of all hosts that is part of the application, with an alias for each of them. The aliases are used in services.xml to define which services is to be started on which nodes.

Deploying applications

After the application package has been constructed, it is deployed using vespa-deploy. This uploads the package to the configuration cluster and pushes the configuration to all nodes. After this, the Vespa cluster is now configured and ready for use.

One of the nice features is that new configurations are loaded without service disruption. When a new application package is deployed, the configuration pushes the new generation to all the defined nodes in the application, which consume and effectuate the new configuration without restarting the services. There are some rare cases that require a restart, the vespa-deploy command will notify when this is needed.

Writing data to Vespa

One of the required files when setting up a Vespa application is the search definition. This file (or files) contains a document definition which defines the fields and their data types for each document type. Data is written to Vespa using Vespa's JSON document format. The data in this format must match the search definition for the document type.

The process of writing data to Vespa is called feeding, and there are multiple tools that can be used to feed data to Vespa for various use cases. For instance there is a REST API for smaller updates and a Java client that can be embedded into other applications.

An important concept in writing data to Vespa is that of document processors. These processors can be chained together to form a processing pipeline to process each document before indexing. This is useful for many use cases, including enrichment by pulling in relevant data from other sources.

Querying Vespa

If you know the id of the document you want, you can fetch it directly using the document API. However, with Vespa you are usually more interested in searching for relevant documents given some query.

Basic querying in Vespa is done through YQL which is an SQL-like language. An example is:

select title,isbn from music where artist contains "kygo";

Here we select the fields "title" and "isbn" from document type "music" where the field called "artist" contains the string "kygo". Wildcards (*) are supported in the result fields and the document types to return all available fields in all defined document types.

The example above shows how to send a query to Vespa over HTTP. Many applications choose to build the queries in Java components running inside Vespa instead. Such components are called searchers, and can be used to build or modify queries, run multiple queries for each incoming request and filter and modify results. Similar to the document processor chains, you can set up chains of searchers. Vespa contains a set of default Searchers which does various common operations such as stemming and federation to multiple content clusters.

Ranking models

Ranking executes a ranking expression specified in the search definition on all the documents matching a query. When returning specific documents for a query, those with the highest rank score are returned.

A ranking expression is a mathematical function over features (named values).

Features are either sent with the query, attributes of the document, constants in the application package or features computed by Vespa from both the query and document - example:

rank-profile popularity inherits default { first-phase { expression: 0.7 * nativeRank(title, description) + 0.3 * attribute(popularity) } }

Here, each document is ranked by the nativeRank function but boosted by a popularity score. This score can be updated at regular intervals, for instance from user feedback, using partial document updates from some external system such as a Hadoop cluster.

In real applications ranking expressions often get much more complicated than this.

For example, a recommendation application may use a deep neural net to compute a recommendation score, or a search application may use a machine-learned gradient boosted decision tree. To support such complex models, Vespa allows ranking expressions to compute over tensors in addition to scalars. This makes it possible to work effectively with large models and parameter spaces.

As complex ranking models can be expensive to compute over many documents, it is often a good idea to use a cheaper function to find good candidates and then rank only those using the full model. To do this you can configure both a first-phase and second-phase ranking expression, where the second-phase function is only computed on the best candidate documents.

Grouping and aggregation

In addition to returning the set of results ordered by a relevance score, Vespa can group and aggregate data over all the documents selected by a query. Common use cases include:

Group documents by unique value of some field.

Group documents by time and date, for instance sort bug tickets by date of creation into the buckets Today, Past Week, Past Month, Past Year, and Everything else.

Calculate the minimum/maximum/average value for a given field.

Groups can be nested arbitrarily and multiple groupings and aggregations can be executed in the same query.

More information

You should now have a basic understanding of the core concepts in building Vespa applications. To try out these core features in practice, head on over to the blog search and recommendation tutorial. We’ll post some more in-depth blog posts with concrete examples soon.

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hptposts · 6 years ago

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Day 2.

Hix hôm nay lại là ngày thứ 7 của tuần tiếp theo.

Mình quên mât viết post hằng ngày rồi @@.

Từ hôm nay sẽ chấn chỉnh lại nha...

Công việc của hôm nay:

+ Giải 10 round của atcoder 042 -> 052

+ Giải 2 round của topcoder

Một kỹ năng quan trọng mình thấy cần nữa là ghi nhớ, mình tạm sẽ ghi những thứ cần ghi nhớ ở đây, chiến thuật sẽ trình bày luôn. Cứ theo chiến thuật mà luyện tập:

+ Ngoài ra thì mình còn muốn học thêm kỹ năng software engineer từ A-Z, ko chỉ làm công việc ở cấp thấp nhất là code nữa...:

Thu thập requirement -> Phân tích -> Tìm giải pháp, hướng tiếp cận -> thiết kế usecase -> Thiết kế kiến trúc UML, quan hệ -> TDD viết test trước -> code theo bản thiết kế.

--> Để code ko có bug, cần tìm hiểu nhiều sách và thực hành code nhiều hơn: Sách mình sẽ đọc tiếp theo về code:

- Clean code

- Code complete

- Working with legacy code

- pattern of enterprise software

- concurrency in practice

Sách về ghi nhớ:

- Mega memory.

Quy trình đọc sách:

Tóm tắt mục lục trong 1 tờ giấy a4 sơ đồ tư duy, ghi nhớ sơ đồ và các ý chính, ngữ cảnh liên quan trong nó. Xong tập vẽ lại sơ đồ 10 lần (1 lần sau 30 phút, 1 lần sau 6h, 1 lần sau 1 ngày, 1 lần 1 tuần, 1 lần tháng)

Áp dụng trong công việc thường xuyên.

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Ok sáng giờ mình xem lời giải của 4 contest atcoder rồi, giờ xem tiếp để tý viết code giải thử.

Cảm nghĩ: Sao thấy bài A,B của 4 contest này cực dễ ak, bài C thì có lúc dễ lúc khó, bài D thì trung bình. Chắc mấy contest đầu cho thả cửa, mấy contest sau bích luôn.

Xem lại phim Baki thôi, muốn tập võ lại thật luôn :D.

OK Table of contents đây rồi

Sách đầu tiên về code sẽ là clean code:

Clean Code TOC

The table of contents of the book Clean Code: A Handbook of Agile Software Craftsmanship (Robert C. Martin, 1994). It is a good overview of the rules recommended by the book.

Contents

Clean Code

There Will Be Code

Bad Code

The Total Cost of Owning a Mess

Schools of Thought

We Are Authors

The Boy Scout Rule

Prequel and Principles

Conclusion

Bibliography

The Grand Redesign in the Sky

Attitude

The Primal Conundrum

The Art of Clean Code?

What Is Clean Code?

Meaningful Names

Introduction

Use Intention-Revealing Names

Avoid Disinformation

Make Meaningful Distinctions

Use Pronounceable Names

Use Searchable Names

Avoid Encodings

Avoid Mental Mapping

Class Names

Method Names

Don’t Be Cute

Pick One Word per Concept

Don’t Pun

Use Solution Domain Names

Use Problem Domain Names

Add Meaningful Context

Don’t Add Gratuitous Context

Final Words

Hungarian Notation

Member Prefixes

Interfaces and Implementations

Functions

Small!

Do One Thing

One Level of Abstraction per Function

Switch Statements

Use Descriptive Names

Function Arguments

Have No Side Effects

Command Query Separation

Prefer Exceptions to Returning Error Codes

Don’t Repeat Yourself

Structured Programming

How Do You Write Functions Like This?

Conclusion

SetupTeardownIncluder

Bibliography

Blocks and Indenting

Sections within Functions

Reading Code from Top to Bottom: The Stepdown Rule

Common Monadic Forms

Flag Arguments

Dyadic Functions

Triads

Argument Objects

Argument Lists

Verbs and Keywords

Output Arguments

Extract Try/Catch Blocks

Error Handling Is One Thing

The Error.java Dependency Magnet

Comments

Comments Do Not Make Up for Bad Code

Explain Yourself in Code

Good Comments

Bad Comments

Bibliography

Legal Comments

Informative Comments

Explanation of Intent

Clarification

Warning of Consequences

TODO Comments

Amplification

Javadocs in Public APIs

Mumbling

Redundant Comments

Misleading Comments

Mandated Comments

Journal Comments

Noise Comments

Scary Noise

Don’t Use a Comment When You Can Use a

Function or a Variable

Position Markers

Closing Brace Comments

Attributions and Bylines

Commented-Out Code

HTML Comments

Nonlocal Information

Too Much Information

Inobvious Connection

Function Headers

Javadocs in Nonpublic Code

Example

Formatting

The Purpose of Formatting

Vertical Formatting

Team Rules

Uncle Bob’s Formatting Rules

The Newspaper Metaphor

Vertical Openness Between Concepts

Vertical Density

Vertical Distance

Vertical Ordering

Horizontal Formatting

Horizontal Openness and Density

Horizontal Alignment

Indentation

Dummy Scopes

Objects and Data Structures

Data Abstraction

Data/Object Anti-Symmetry

The Law of Demeter

Data Transfer Objects

Conclusion

Bibliography

Train Wrecks

Hybrids

Hiding Structure

Active Record

Error Handling

Use Exceptions Rather Than Return Codes

Write Your Try-Catch-Finally Statement First

Use Unchecked Exceptions

Provide Context with Exceptions

Define Exception Classes in Terms of a Caller’s Needs

Define the Normal Flow

Don’t Return Null

Don’t Pass Null

Conclusion

Bibliography

Boundaries

Using Third-Party Code

Exploring and Learning Boundaries

Learning log4j

Learning Tests Are Better Than Free

Using Code That Does Not Yet Exist

Clean Boundaries

Bibliography

Unit Tests

The Three Laws of TDD

Keeping Tests Clean

Clean Tests

One Assert per Test

F.I.R.S.T

Conclusion

Bibliography

Tests Enable the -ilities

Domain-Specific Testing Language

A Dual Standard

Single Concept per Test

Classes

Class Organization

Classes Should Be Small!

Organizing for Change

Bibliography

Encapsulation

The Single Responsibility Principle

Cohesion

Maintaining Cohesion Results in Many Small Classes

Isolating from Change

Systems

How Would You Build a City?

Separate Constructing a System from Using It

Scaling Up

Java Proxies

Pure Java AOP Frameworks

AspectJ Aspects

Test Drive the System Architecture

Optimize Decision Making

Use Standards Wisely, When They Add DemonstrableValue

Systems Need Domain-Specific Languages

Conclusion

Bibliography

Separation of Main

Factories

Dependency Injection

Cross-Cutting Concerns

Emergence

Getting Clean via Emergent Design

Simple Design Rule 1: Runs All the Tests

Simple Design Rules 2–4: Refactoring

No Duplication

Expressive

Minimal Classes and Methods

Conclusion

Bibliography

Concurrency

Why Concurrency?

Myths and Misconceptions

Challenges

Concurrency Defense Principles

Know Your Library

Know Your Execution Models

Beware Dependencies Between Synchronized Methods

Keep Synchronized Sections Small

Writing Correct Shut-Down Code Is Hard

Testing Threaded Code

Conclusion

Bibliography

Single Responsibility Principle

Corollary: Limit the Scope of Data

Corollary: Use Copies of Data

Corollary: Threads Should Be as Independent as Possible

Thread-Safe Collections

Producer-Consumer

Readers-Writers

Dining Philosophers

Treat Spurious Failures as Candidate Threading Issues

Get Your Nonthreaded Code Working First

Make Your Threaded Code Pluggable

Make Your Threaded Code Tunable

Run with More Threads Than Processors

Run on Different Platforms

Instrument Your Code to Try and Force Failures

Hand-Coded

Automated

Successive Refinement

Args Implementation

Args: The Rough Draft

String Arguments

Conclusion

How Did I Do This?

So I Stopped

On Incrementalism

JUnit Internals

The JUnit Framework

Conclusion

Refactoring SerialDate

First, Make It Work

Then Make It Right

Conclusion

Bibliography

Smells and Heuristics

Comments

Environment

Functions

General

Java

Names

Tests

Conclusion

Bibliography

Inappropriate Information

Obsolete Comment

Redundant Comment

Poorly Written Comment

Commented-Out Code

Build Requires More Than One Step

Tests Require More Than One Step

Too Many Arguments

Output Arguments

Flag Arguments

Dead Function

Multiple Languages in One Source File

Obvious Behavior Is Unimplemented

Incorrect Behavior at the Boundaries

Overridden Safeties

Duplication

Code at Wrong Level of Abstraction

Base Classes Depending on Their Derivatives

Too Much Information

Dead Code

Vertical Separation

Inconsistency

Clutter

Artificial Coupling

Feature Envy

Selector Arguments

Obscured Intent

Misplaced Responsibility

Inappropriate Static

Use Explanatory Variables

Function Names Should Say What They Do

Understand the Algorithm

Make Logical Dependencies Physical

Prefer Polymorphism to If/Else or Switch/Case

Follow Standard Conventions

Replace Magic Numbers with Named Constants

Be Precise

Structure over Convention

Encapsulate Conditionals

Avoid Negative Conditionals

Functions Should Do One Thing

Hidden Temporal Couplings

Don’t Be Arbitrary

Encapsulate Boundary Conditions

Functions Should Descend Only One Level of Abstraction

Keep Configurable Data at High Levels

Avoid Transitive Navigation

Avoid Long Import Lists by Using Wildcards

Don’t Inherit Constants

Constants versus Enums

Choose Descriptive Names

Choose Names at the Appropriate Level of Abstraction

Use Standard Nomenclature Where Possible

Unambiguous Names

Use Long Names for Long Scopes

Avoid Encodings

Names Should Describe Side-Effects.

Insufficient Tests

Use a Coverage Tool!

Don’t Skip Trivial Tests

An Ignored Test Is a Question about an Ambiguity

Test Boundary Conditions

Exhaustively Test Near Bugs

Patterns of Failure Are Revealing

Test Coverage Patterns Can Be Revealing

Tests Should Be Fast

Appendix A: Concurrency II

Client/Server Example

Possible Paths of Execution

Knowing Your Library

Dependencies Between Methods

Can Break Concurrent Code

Increasing Throughput

Deadlock

Testing Multithreaded Code

Tool Support for Testing Thread-Based Code

Conclusion

Tutorial: Full Code Examples

The Server

Adding Threading

Server Observations

Conclusion

Number of Paths

Digging Deeper

Conclusion

Executor Framework

Nonblocking Solutions

Nonthread-Safe Classes

Tolerate the Failure

Client-Based Locking

Server-Based Locking

Single-Thread Calculation of Throughput

Multithread Calculation of Throughput

Mutual Exclusion

Lock & Wait

No Preemption

Circular Wait

Breaking Mutual Exclusion

Breaking Lock & Wait

Breaking Preemption

Breaking Circular Wait

Client/Server Nonthreaded

Client/Server Using Threads

Appendix B: org.jfree.date.SerialDate

Appendix C: Cross References of Heuristics

Epilogue

----

+Code complete TOC +Software Estimation: The Art

+Rapid Development: Taming Wild Software Schedules+Rapid Development: Taming Wild Software Schedules

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rafi1228 · 5 years ago

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A guide to understand generics, basic collections and reflection in Java!

What you’ll learn

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Implement generic algorithms (data structures, graph algorithms etc.)

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Requirements

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Basic Java ( loops, classes etc. )

Description

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stacks and queues

sets and maps

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The post Introduction to Collections & Generics in Java appeared first on Free Course Lab.

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raj89100 · 6 years ago

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robertbryantblog · 6 years ago

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quickclickhosting · 6 years ago

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korn-for-all-life-blog · 8 years ago

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Patch is just behind us in the case of Microsoft and Adobe, and just ahead of us in the case of Oracle.

As regular Naked Security reader Haemish Edgerton pointed out to us, Adobe updated both Flash and Shockwave Player (for those of you still using it), but only the Flash update involves security fixes, so there was only one Adobe security bulletin this month.

Three CVEs (officially-numbered vulnerabilities) are listed amongst the bugs fixed in the Flash update.

Two of the CVEs, namely CVE-2014-0537 and CVE-2014-0539, weren’t publicly disclosed holes, and weren’t remote code execution vulnerabilities.

Unfortunately, the third CVE relates to a vulnerability that is now being popularised, like Heartbleed, with a catchy name and logo by the Google researcher who worked out how to exploit it.

Michele Spagnuolo has dubbed his exploit “Rosetta”, by analogy with the Rosetta Stone that helped linguists decipher early Egyptian script, because it works by translating Flash files into 100% printable alphanumeric characters.

The “Rosetta” exploit, officially tagged as CVE-2014-4671, is what’s known as a Cross Site Request Forgery, or CSRF, meaning that it provides a way for malicious website X to retrieve data that is only supposed to be revealed when you visit site Y.

According to Adobe, the Flash update for July 2014 update also fixes “vulnerabilities that could potentially allow an attacker to take control of the affected system.”

That’s longhand for remote code execution (RCE) or click-to-own, where a crook implants malware on your computer without so much as a by-your-leave.

We suggest that you apply this Flash update as soon as you possibly can, not just because of the RCE holes, but because Spagnuolo has now gone public with a detailed description of the Rosetta attack.

Spagnuolo has also published what he refers to as “ready-to-be-pasted, universal, weaponized full featured proofs of concept with ActionScript sources.”

Heigh-ho.

If you are relying on Adobe’s auto-updating process, the new Flash Player version numbers to look out for are 11.2.202.394 on Linux, and 14.0.0.145 on Windows and OS X.

NB. Sophos products detect and block Flash files made with Spagnuolo’s “Rosetta Flash” conversion tools as Troj/RosFlash-A.

MICROSOFT’S PATCHES

Microsoft published six bulletins this month, matching what it announced in advance.

The update that most users will be immediately interested in is Bulletin One, a Cumulative Security Update for Internet Explorer that gets the identifier MS14-037.

This is a critical fix because it patches RCE holes, as well as various other bugs, so don’t delay in applying it.

Fortunately, however, the RCE flaws are amongst some of the 23 vulnerabilities that were responsibly disclosed, none of which has been seen in the wild.

Only one of this month’s vulnerabilities in IE was publicly known in advance of the patches, and is nevertheless not known to have been exploited in real-world attacks.

The publicly-disclosed hole is known as CVE-2014-2783, and has been dubbed an “Extended Validation SSL Certificate” vulnerability.

Briefly put, so-called Extended Validation (EV) HTTPS certificates are supposed to apply to specific server names only.

So a rogue Certificate Authority that fell in with crooks, or was under pressure from its country’s intelligence service, or had its private keys stolen, would be throttled to issuing one dodgy EV certificate at a time.

If the untrustworthy CA tried to create an EV certificate for, say, *.example.com instead of justthisone.example.com, browsers should reject that certificate, considering the wildcard to be below the standards required for extended validation.

JNT – A NEW RISKY FILE TYPE

But for all the obvious importance of Microsoft’s IE update, it is the second critical fix, MS14-038, that is the most intriguing, and perhaps even more important, patch.

This closes a single, privately-disclosed, parsing flaw in Microsoft Journal (JNT) files.

I’ll be honest and admit that I wasn’t even aware of .JNT files, or the application JOURNAL.EXE (installed by default on non-server flavours of Windows), until this vulnerability was announced.

Journal is a note-taking application that lets you scribble down notes as if on a piece of paper, and share them in them as .JNT files with other people.

Anyway, deliberately-crafted Journal files can be made to crash the Journal software in a way that could give an attacker remote control of your computer, for example by persauding you to open a .JNTattachment in an email.

In short: apply the patch.

And, if you weren’t aware of .JNT files as yet another proprietary Windows document exchange type, then you almost certainly aren’t deliberately using the Journal application, so consider adding .JNTto your web and email file filtering blocklist.

ELEVATION OF PRIVILEGE

Three of the other flaws patched by Microsoft are so-called Elevation of Privilege (EoP) holes, two of which allow local users to “promote” themselves to kernel-level privilege.

As usual, these flaws only get an Important rating, instead of Critical, mainly because they can’t be directly exploited from outside your network, or even inside your network by someone who isn’t logged in.

However, I’m sticking to my opinion that this sort of hole is probably somewhere closer to Criticalthan Important, simply because of the advantage, to crooks who are already inside your network, of being able to get kernel-level privileges at will.

There are two obvious abuse scenarios for EoP-to-kernel exploits:

By rogue insiders. Users who have not been given administrator privileges on their own computers can unofficially acquire those rights in unauthorised, and quite possibly unauditable, ways. That’s hard for IT to control or even to detect using its regular tools.

By malware seeking to install a rootkit. Rootkits are add-on modules that add what you might call tamper protection to malware, often making it harder to detect and remove. Making users non-administrators usually keeps rootkits out.

ORACLE’S PATCHES

Finally, to wrap up this overview, we’ll mention Oracle.

Oracle’s patching drum beats to a different rhythm, using the Tuesday closest to the middle of the month, not the second Tuesday as with Microsoft and Adobe.

So Oracle’s July 2014 updates have yet to drop, but we do know one thing: support for Java on Windows XP is over.

In Oracle’s own words, Java 8 won’t work at all on XP, but users “may still continue to use Java 7 updates on Windows XP at their own risk.”

As my friend and colleague Chester Wisniewski twittily quipped,

Of course, the truth is that the sort of users who are sticking with a now-unsupported XP “because they can” are likely to end up even less secure, by sticking with a now-unsupported Java as well.

Still got Java in your browser?

Try turning it off and seeing if any websites stop working – the chance is good that nothing will break and you can leave it off for evermore.

source:https://nakedsecurity.sophos.com/2014/07/09/patch-tuesday-wrap-up-july-2014-adobe-fixes-rosetta-plus-a-new-risky-file-type-on-windows/

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rafi1228 · 5 years ago

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Java Collections – List Interface(ArrayList, LinkedList and Vector), Set Interface (HashSet, LinkedHashSet and TreeSet), Queue Interface (PriorityQueue) and Map Interface (HashMap, HashTable, LinkedHashMap and TreeMap() – Compare, Contrast and Choose

Generics – Why do we need Generics? Restrictions with extends and Generic Methods, WildCards – Upper Bound and Lower Bound.

Functional Programming – Lambda Expression, Stream and Operations on a Stream (Intermediate Operations – Sort, Distinct, Filter, Map and Terminal Operations – max, min, collect to List), Functional Interfaces – Predicate Interface,Consumer Interface, Function Inteface for Mapping, Method References – static and instance methods

Introduction to Threads and MultiThreading – Need for Threads

Implementing Threads – Extending Thread Class and Implementing Runnable Interface

States of a Thread and Communication between Threads

Introduction to Executor Service – Customizing number of Active Threads. Returning a Future, invokeAll and invokeAny

Introduction to Exception Handling – Your Thought Process during Exception Handling. try, catch and finally. Exception Hierarchy – Checked Exceptions vs Unchecked Exceptions. Throwing an Exception. Creating and Throwing a Custom Exception – CurrenciesDoNotMatchException. Try with Resources – New Feature in Java 7.

List files and folders in Directory with Files list method, File walk method and find methods. Read and write from a File.

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******* Step By Step Details *******

Introduction to Java Programming with Jshell using Multiplication Table

Step 00 – Getting Started with Programming Step 01 – Introduction to Multiplication Table challenge Step 02 – Launch JShell Step 03 – Break Down Multiplication Table Challenge Step 04 – Java Expression – An Introduction Step 05 – Java Expression – Exercises Step 06 – Java Expression – Puzzles Step 07 – Printing output to console with Java Step 08 – Printing output to console with Java – Exercise Statements Step 09 – Printing output to console with Java – Exercise Solutions Step 10 – Printing output to console with Java – Puzzles Step 11 – Advanced Printing output to console with Java Step 12 – Advanced Printing output to console with Java – Exercises and Puzzles Step 13 – Introduction to Variables in Java Step 14 – Introduction to Variables in Java – Exercises and Puzzles Step 15 – 4 Important Things to Know about Variables in Java Step 16 – How are variables stored in memory? Step 17 – How to name a variable? Step 18 – Understanding Primitive Variable Types in Java Step 19 – Understanding Primitive Variable Types in Java – Choosing a Type Step 20 – Java Assignment Operator Step 21 – Java Assignment Operator – Puzzles on Increment, Decrement and Compound Assignment Step 23 – Java Conditionals and If Statement – Introduction Step 24 – Java Conditionals and If Statement – Exercise Statements Step 25 – Java Conditionals and If Statement – Exercise Solutions Step 26 – Java Conditionals and If Statement – Puzzles Step 27 – Java For Loop to Print Multiplication Table – Introduction Step 28 – Java For Loop to Print Multiplication Table – Exercise Statements Step 29 – Java For Loop to Print Multiplication Table – Exercise Solutions Step 30 – Java For Loop to Print Multiplication Table – Puzzles Step 31 – Programming Tips : JShell – Shortcuts, Multiple Lines and Variables TODO Move up Step 32 – Getting Started with Programming – Revise all Terminology

Introduction to Method with Multiplication Table

Step 00 – Section 02 – Methods – An Introduction Step 01 – Your First Java Method – Hello World Twice and Exercise Statements Step 02 – Introduction to Java Methods – Exercises and Puzzles Step 03 – Programming Tip – Editing Methods with JShell Step 04 – Introduction to Java Methods – Arguments and Parameters Step 05 – Introduction to Java Method Arguments – Exercises Step 06 – Introduction to Java Method Arguments – Puzzles and Tips Step 07 – Getting back to Multiplication Table – Creating a method Step 08 – Print Multiplication Table with a Parameter and Method Overloading Step 09 – Passing Multiple Parameters to a Java Method Step 10 – Returning from a Java Method – An Introduction Step 11 – Returning from a Java Method – Exercises Step 99 – Methods – Section Review

Introduction to Java Platform

Step 00 – Section 03 – Overview Of Java Platform – Section Overview Step 01 – Overview Of Java Platform – An Introduction – java, javac, bytecode and JVM Step 02 – Java Class and Object – First Look Step 03 – Create a method in a Java class Step 04 – Create and Compile Planet.java class Step 05 – Run Planet calss with Java – Using a main method Step 06 – Play and Learn with Planet Class Step 07 – JDK vs JRE vs JVM

Introduction to Eclipse – First Java Project

Step 01 – Creating a New Java Project with Eclipse Step 02 – Your first Java class with Eclipse Step 03 – Writing Multiplication Table Java Program with Eclipse Step 04 – Adding more methods for Multiplication Table Program Step 05 – Programming Tip 1 : Refactoring with Eclipse Step 06 – Programming Tip 2 : Debugging with Eclipse Step 07 – Programming Tip 3 : Eclipse vs JShell – How to choose?

Introduction To Object Oriented Programming

Step 00 – Introduction to Object Oriented Programming – Section Overview Step 01 – Introduction to Object Oriented Programming – Basics Step 02 – Introduction to Object Oriented Programming – Terminology – Class, Object, State and Behavior Step 03 – Introduction to Object Oriented Programming – Exercise – Online Shopping System and Person Step 04 – Create Motor Bike Java Class and a couple of objects Step 05 – Exercise Solutions – Book class and Three instances Step 06 – Introducing State of an object with speed variable Step 07 – Understanding basics of Encapsulation with Setter methods Step 08 – Exercises and Tips – Getters and Generating Getters and Setters with Eclipse Step 09 – Puzzles on this and initialization of member variables Step 10 – First Advantage of Encapsulation Step 11 – Introduction to Encapsulation – Level 2 Step 12 – Encapsulation Exercises – Better Validation and Book class Step 13 – Introdcution to Abstraction Step 14 – Introduction to Java Constructors Step 15 – Introduction to Java Constructors – Exercises and Puzzles Step 16 – Introduction to Object Oriented Programming – Conclusion

Primitive Data Types And Alternatives

Step 00 – Primitive Data Types in Depth – Section Overview Step 01 – Basics about Java Integer Data Types – Casting, Operators and More Step 02 – Java Integer Data Types – Puzzles – Octal, Hexadecimal, Post and Pre increment Step 03 – Java Integer Data Types – Exercises – BiNumber – add, multiply and double Step 04 – Java Floating Point Data Types – Casting , Conversion and Accuracy Step 05 – Introduction to BigDecimal Java Class Step 06 – BigDecimal Puzzles – Adding Integers Step 07 – BigDecimal Exercises – Simple Interest Calculation Step 08 – Java Boolean Data Type – Relational and Logical Operators Step 09 – Java Boolean Data Type – Puzzles – Short Circuit Operators Step 10 – Java Character Data Type char – Representation and Conversion Step 11 – Java char Data Type – Exercises 1 – isVowel Step 12 – Java char Data Type – Exercises 2 – isDigit Step 13 – Java char Data Type – Exercises 3 – isConsonant, List Upper Case and Lower Case Characters Step 14 – Primitive Data Types in Depth – Conclusion

Conditionals

Step 00 – Conditionals with Java – Section Overview Step 01 – Introduction to If Else Statement Step 02 – Introduction to Nested If Else Step 03 – If Else Statement – Puzzles Step 04 – If Else Problem – How to get User Input in Java? Step 05 – If Else Problem – How to get number 2 and choice from user? Step 06 – If Else Problem – Implementing with Nested If Else Step 07 – Java Switch Statement – An introduction Step 08 – Java Switch Statement – Puzzles – Default, Break and Fall Through Step 09 – Java Switch Statement – Exercises – isWeekDay, nameOfMonth, nameOfDay Step 10 – Java Ternary Operation – An Introduction Step 11 – Conditionals with Java – Conclusion

Loops

Step 00 – Java Loops – Section Introduction Step 01 – Java For Loop – Syntax and Puzzles Step 02 – Java For Loop – Exercises Overview and First Exercise Prime Numbers Step 03 – Java For Loop – Exercise – Sum Upto N Numbers and Sum of Divisors Step 04 – Java For Loop – Exercise – Print a Number Triangle Step 05 – While Loop in Java – An Introduction Step 06 – While Loop – Exericises – Cubes and Squares upto limit Step 07 – Do While Loop in Java – An Introduction Step 08 – Do While Loop in Java – An Example – Cube while user enters positive numbers Step 09 – Introduction to Break and Continue Step 10 – Selecting Loop in Java – For vs While vs Do While

Reference Types

Step 00 – Java Reference Types – Section Introduction Step 01 – Reference Types – How are they stored in Memory? Step 02 – Java Reference Types – Puzzles Step 03 – String class – Introduction and Exercise – Print each word and char on a new line Step 04 – String class – Exercise Solution and Some More Important Methods Step 05 – Understanding String is Immutable and String Concat, Upper Case, Lower Case, Trim methods Step 06 – String Concatenation and Join, Replace Methods Step 07 – Java String Alternatives – StringBuffer and StringBuilder Step 08 – Java Wrapper Classes – An Introduction – Why and What? Step 09 – Java Wrapper Classes – Creation – Constructor and valueOf Step 10 – Java Wrapper Classes – Auto Boxing and a Few Wrapper Constants – SIZE, BYTES, MAX_VALUE and MIN_VALUE Step 11 – Java Dates – Introduction to LocalDate, LocalTime and LocalDateTime Step 12 – Java Dates – Exploring LocalDate – Creation and Methods to play with Date Step 13 – Java Dates – Exploring LocalDate – Comparing Dates and Creating Specific Dates Step 14 – Java Reference Types – Conclusion

Arrays and ArrayLists

Step 00 – Introduction to Array and ArrayList – Section Introduction with a Challenge Step 01 – Understanding the need and Basics about an Array Step 02 – Java Arrays – Creating and Accessing Values – Introduction Step 03 – Java Arrays – Puzzles – Arrays of Objects, Primitive Data Types, toString and Exceptions Step 04 – Java Arrays – Compare, Sort and Fill Step 05 – Java Arrays – Exercise – Create Student Class – Part 1 – Total and Average Marks Step 06 – Java Arrays – Exercise – Create Student Class – Part 2 – Maximum and Minimum Mark Step 07 – Introduction to Variable Arguments – Need Step 08 – Introduction to Variable Arguments – Basics Step 09 – Introduction to Variable Arguments – Enhancing Student Class Step 10 – Java Arrays – Using Person Objects and String Elements with Exercises Step 11 – Java String Arrays – Exercise Solutions – Print Day of Week with Most number of letters and more Step 12 – Adding and Removing Marks – Problem with Arrays Step 13 – First Look at ArrayList – An Introduction Step 14 – First Look at ArrayList – Refactoring Student Class to use ArrayList Step 15 – First Look at ArrayList – Enhancing Student Class with Add and Remove Marks Step 16 – Introduction to Array and ArrayList – Conclusion

Object Oriented Programming Again

Step 00 – Object Oriented Programming – Level 2 – Section Introduction Step 01 – Basics of Designing a Class – Class, Object, State and Behavior Step 02 – OOPS Example – Fan Class – Deciding State and Constructors Step 03 – OOPS Example – Fan Class – Deciding Behavior with Methods Step 04 – OOPS Exercise – Rectangle Class Step 05 – Understanding Object Composition with Customer Address Example Step 06 – Understanding Object Composition – An Exercise – Books and Reviews Step 07 – Understanding Inheritance – Why do we need it? Step 08 – Object is at top of Inheritance Hierarchy Step 09 – Inheritance and Overriding – with toString() method Step 10 – Java Inheritance – Exercise – Student and Employee Classes Step 11 – Java Inheritance – Default Constructors and super() method call Step 12 – Java Inheritance – Puzzles – Multiple Inheritance, Reference Variables and instanceof Step 13 – Java Abstract Class – Introductio Step 14 – Java Abstract Class – First Example – Creating Recipes with Template Method Step 15 – Java Abstract Class – Puzzles Step 16 – Java Interface – Example 1 – Gaming Console – How to think about Intefaces? Step 17 – Java Interface – Example 2 – Complex Algorithm – API defined by external team Step 18 – Java Interface – Puzzles – Unimplemented methods, Abstract Classes, Variables, Default Methods and more Step 19 – Java Interface vs Abstract Class – A Comparison Step 20 – Java Interface Flyable and Abstract Class Animal – An Exercise Step 21 – Polymorphism – An introduction

Collections

Step 01 – Java Collections – Section Overview with Need For Collections Step 02 – List Interface – Introduction – Position is King Step 03 – List Inteface – Immutability and Introduction of Implementations – ArrayList, LinkedList and Vector Step 04 – List Inteface Implementations – ArrayList vs LinkedList Step 05 – List Inteface Implementations – ArrayList vs Vector Step 06 – List Inteface – Methods to add, remove and change elements and lists Step 07 – List and ArrayList – Iterating around elements Step 08 – List and ArrayList – Choosing iteration approach for printing and deleting elements Step 09 – List and ArrayList – Puzzles – Type Safety and Removing Integers Step 10 – List and ArrayList – Sorting – Introduction to Collections sort static method Step 11 – List and ArrayList – Sorting – Implementing Comparable Inteface in Student Class Step 12 – List and ArrayList – Sorting – Providing Flexibility by implementing Comparator interface Step 13 – List and ArrayList – A Summary Step 14 – Set Interface – Introduction – No Duplication Step 15 – Understanding Data Structures – Array, LinkedList and Hashing Step 16 – Understanding Data Structures – Tree – Sorted Order Step 17 – Set Interface – Hands on – HashSet, LinkedHashSet and TreeSet Step 18 – Set Interface – Exercise – Find Unique Characters in a List Step 19 – TreeSet – Methods from NavigableSet – floor,lower,upper, subSet, head and tailSet Step 20 – Queue Interface – Process Elements in Order Step 21 – Introduction to PriorityQueue – Basic Methods and Customized Priority Step 22 – Map Interface – An Introduction – Key and Value Step 23 – Map Interface – Implementations – HashMap, HashTable, LinkedHashMap and TreeMap Step 24 – Map Interface – Basic Operations Step 25 – Map Interface – Comparison – HashMap vs LinkedHashMap vs TreeMap Step 26 – Map Interface – Exercise – Count occurances of characters and words in a piece of text Step 27 – TreeMap – Methods from NavigableMap – floorKey, higherKey, firstEntry, subMap and more Step 28 – Java Collections – Conclusion with Three Tips

Generics

Step 01 – Introduction to Generics – Why do we need Generics? Step 02 – Implementing Generics for the Custom List Step 03 – Extending Custom List with a Generic Return Method Step 04 – Generics Puzzles – Restrictions with extends and Generic Methods Step 05 – Generics and WildCards – Upper Bound and Lower Bound

Introduction to Functional Programming

Step 01 – Introduction to Functional Programming – Functions are First Class Citizens Step 02 – Functional Programming – First Example with Function as Parameter Step 03 – Functional Programming – Exercise – Loop a List of Numbers Step 04 – Functional Programming – Filtering – Exercises to print odd and even numbers from List Step 05 – Functional Programming – Collect – Sum of Numbers in a List Step 06 – Functional Programming vs Structural Programming – A Quick Comparison Step 07 – Functional Programming Terminology – Lambda Expression, Stream and Operations on a Stream Step 08 – Stream Intermediate Operations – Sort, Distinct, Filter and Map Step 09 – Stream Intermediate Operations – Exercises – Squares of First 10, Map String List to LowerCase and Length of String Step 10 – Stream Terminal Operations – 1 – max operation with Comparator Step 11 – Stream Terminal Operations – 2 – min, collect to List, Step 12 – Optional class in Java – An Introduction Step 13 – Behind the Screens with Functional Interfaces – Implement Predicate Interface Step 14 – Behind the Screens with Functional Interfaces – Implement Consumer Interface Step 15 – Behind the Screens with Functional Interfaces – Implement Function Inteface for Mapping Step 16 – Simplify Functional Programming code with Method References – static and instance methods Step 17 – Functions are First Class Citizens Step 18 – Introduction to Functional Programming – Conclusion

Introduction to Threads And Concurrency

Step 01 – Introduction to Threads and MultiThreading – Need for Threads Step 02 – Creating a Thread for Task1 – Extending Thread Class Step 03 – Creating a Thread for Task2 – Implement Runnable Interface Step 04 – Theory – States of a Thread Step 05 – Placing Priority Requests for Threads Step 06 – Communication between Threads – join method Step 07 – Thread utility methods and synchronized keyword – sleep, yield Step 08 – Need for Controlling the Execution of Threads Step 09 – Introduction to Executor Service Step 10 – Executor Service – Customizing number of Threads Step 11 – Executor Service – Returning a Future from Thread using Callable Step 12 – Executor Service – Waiting for completion of multiple tasks using invokeAll Step 13 – Executor Service – Wait for only the fastest task using invokeAny Step 14 – Threads and MultiThreading – Conclusion

Introduction to Exception Handling

Step 01 – Introduction to Exception Handling – Your Thought Process during Exception Handling Step 02 – Basics of Exceptions – NullPointerException and StackTrace Step 03 – Basics of Handling Exceptions – try and catch Step 04 – Basics of Handling Exceptions – Exception Hierarchy, Matching and Catching Multiple Exceptions Step 05 – Basics of Handling Exceptions – Need for finally Step 06 – Basics of Handling Exceptions – Puzzles Step 07 – Checked Exceptions vs Unchecked Exceptions – An Example Step 08 – Hierarchy of Errors and Exceptions – Checked and Runtime Step 09 – Throwing an Exception – Currencies Do Not Match Runtime Exception Step 10 – Throwing a Checked Exception – Throws in method signature and handling Step 11 – Throwing a Custom Exception – CurrenciesDoNotMatchException Step 12 – Write less code with Try with Resources – New Feature in Java 7 Step 13 – Basics of Handling Exceptions – Puzzles 2 Step 14 – Exception Handling – Conclusion with Best Practices

Files and Directories

Step 01 – List files and folders in Directory with Files list method Step 02 – Recursively List and Filter all files and folders in Directory with Step Files walk method and Search with find method Step 03 – Read content from a File – Files readAllLines and lines methods Step 04 – Writing Content to a File – Files write method Step 05 – Files – Conclusion

More Concurrency with Concurrent Collections and Atomic Operations

Step 01 – Getting started with Synchronized Step 02 – Problem with Synchronized – Less Concurrency Step 03 – Enter Locks with ReEntrantLock Step 04 – Introduction to Atomic Classes – AtomicInteger Step 05 – Need for ConcurrentMap Step 06 – Implementing an example with ConcurrentHashMap Step 07 – ConcurrentHashMap uses different locks for diferrent regions Step 08 – CopyOnWrite Concurrent Collections – When reads are more than writes Step 09 – Conclusion

Java Tips

Java Tip 01 – Imports and Static Imports Java Tip 02 – Blocks Java Tip 03 – equals method Java Tip 04 – hashcode method Java Tip 05 – Class Access Modifiers – public and default Java Tip 06 – Method Access Modifiers – public, protected, private and default Java Tip 07 – Final classes and Final methods Java Tip 08 – Final Variables and Final Arguments Java Tip 09 – Why do we need static variables? Java Tip 09 – Why do we need static methods? Java Tip 10 – Static methods cannot use instance methods or variables Java Tip 11 – public static final – Constants Java Tip 12 – Nested Classes – Inner Class vs Static Nested Class Java Tip 13 – Anonymous Classes Java Tip 14 – Why Enum and Enum Basics – ordinal and values Java Tip 15 – Enum – Constructor, variables and methods Java Tip 16 – Quick look at inbuild Enums – Month, DayOfWeek

Zero risk. 30 day money-back guarantee with every purchase of the course. You have nothing to lose!

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Who this course is for:

You have ZERO programming experience and want to learn Java Programming

You are a Beginner at Java Programming and want to Learn to write Great Java Programs

You want to learn the Basics of Object Oriented Programming with Java

You want to learn the Basics of Functional Programming with Java

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rafi1228 · 6 years ago

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Learn Python 3 from scratch! Build your own network scripts and upgrade your Network Engineering skills! Updated 2019.

What you’ll learn

Master all the Python 3 key concepts starting from scratch. No prior Python knowledge is required!

Apply your new Python 3 skills to build various tools for network interaction and make your job easier.

Use Python 3 for connecting via SSH to any network device and reading/writing configuration from multiple devices simultaneously.

Use Python 3 for establishing SSH sessions to network devices, extract parameters like the CPU utilization and build real-time graphs for performance monitoring.

Use Python 3 for building an interactive subnet calculator with a user menu. The tool will return the network and broadcast addresses, the number of valid hosts per subnet, the wildcard mask and will generate random IP addresses from the subnet.

Use Python 3 for building a basic packet sniffer, capturing and analyzing network packets (ARP, ICMP, BOOTP) and saving packet data to a log file.

Use Python 3 for building a configuration change management tool that will extract the running config of a network device at specific time intervals, will compare it to the previous version, detect and highlight all the changes and send the network admin a nice and clean report via e-mail on a daily basis.

Get the full Python 3 code of 5 amazing network applications and customize each of them according to your networking needs.

Get many other useful, free resources to enhance your learning experience: quizzes, notebooks (code samples), cheat sheet (syntax summary and examples), e-book (syntax guide).

Get my Python 2 network programming (legacy) content, as a bonus, at the end of the course. However, you should definitely focus your efforts on the Python 3 content.

Get my full support for any question or issue. Udemy provides you with a 30-day money-back guarantee, full refund, no questions asked and a Certificate of Completion.

Ask for a raise at your current job or apply for a better position using the network automation skills gained from this course.

Requirements

No prior Python knowledge is required! This training teaches your everything, from scratch.

You should have a great desire to learn Python programming and do it in a hands-on fashion, without having to watch countless videos filled with slides and theory.

You should already be familiar with networking concepts like: Switching, TCP/IP, CLI, SSHv2, Telnet, OSI Layers.

You are going to use only free software throughout the course: Python 3.7, VirtualBox, Arista vEOS, Notepad++.

All you need is a decent PC or laptop (2GHz CPU, 8-16GB RAM) and an Internet connection to download the free tools.

Preferably, you should have a Windows OS to work on, to be fully synchronized with the course content.

Description

✔ 25 hours of content designed for Network Engineers

✔ I am updating the course frequently and answering all your questions

✔ Full Python 3 applications, quizzes and notebooks are included

✔ Downloadable Python 3 cheat sheet and 200+ pages PDF e-book are included

✔ Udemy Bestselling Instructor with over 1500 ⭐⭐⭐⭐⭐ reviews

✔ Over 50.000 satisfied students across several e-learning platforms

✔ Certificate of Completion is Included

“Have finished 35% of the course, so far it’s the best Python-for-network-engineer course I have ever attended, fundamental topics are well demonstrated and explained, I strongly recommend this course to any network engineers who want to master Python in a relatively short period of time.” by Parry Wang

✔ What others have to say about my Python courses?

Before you read what I have to say, see what my students are saying about my courses:

“What an incredible value and learning experience!” by Sean A.

“Excellent material. Kudos to a great instructor with a vast level of creativity.” by Anthony W.

“I can say this man is going on smoothly and perfectly, explaining in the most empirical/foundational way.” by Kolapo A.

✔ Why would you take this course?

Do you want to become a Python Developer without having to spend a lot of money on books and boring theoretical courses?

Are you a network professional who wants to start automating network tasks using Python?

Or maybe you’re seeking a raise or even a career change?

Join thousands of successful students who have decided to learn Python, upgrade their networking skills and boost their careers using this 100% hands-on course!

✔ What’s this course all about?

Python Network Programming (version 3.7) course aimed not only at network professionals, but at anyone having little or no experience in coding or network automation and a great desire to start learning Python from scratch. This hands-on Python Network Programming training takes you from “Hello World!” to building complex network applications in no time.

During this course you will learn Python concepts which are relevant to your networking job and build some amazing network tools:

Introduction – What’s This Course All About?

Python 3 – Basics

Python 3 – Strings

Python 3 – Numbers and Booleans

Python 3 – Lists

Python 3 – Sets

Python 3 – Tuples

Python 3 – Ranges

Python 3 – Dictionaries

Python 3 – Conditionals, Loops and Exceptions

Python 3 – Functions and Modules

Python 3 – File Operations

Python 3 – Regular Expressions

Python 3 – Classes and Objects

Python 3 – Advanced Concepts and Tools

Python 3 – Download the Cheat Sheet

Python 3 – Download the E-Book

Setting Up the Working Environment

Network Application #1 – Reading / Writing Device Configuration via SSH

Network Application #2 – Building an Interactive Subnet Calculator

Network Application #3 – Extracting Network Parameters & Building Graphs

Network Application #4 – Building a Basic Network Packet Sniffer

Network Application #5 – Config File Management and E-mail Notifications

Final Section – Get Your Certificate, Let’s Connect on Social Media, Bonuses

Bonus – Python 2 Legacy Content

Sounds unbelievable given your current programming experience? Well, it’s true! How?

First, you will learn and practice every Python 3 key concept, which is explained in one or more video lectures, followed by a short quiz. Each video is filled with relevant examples, in a learn-by-doing fashion and the quizzes will help you consolidate the main ideas behind each Python topic.

After laying the foundation (and also exploring some advanced Python topics), you will dive right into the real-life network scenarios and apply your knowledge to build 5 great network tools using the power of Python.

Equipped with working files, cheat sheets and Python code samples, you will be able to work alongside me on each lecture and each application. I will provide a virtual machine with all the Python modules already installed and also the full code for each application, so you can save time and start coding and testing on the spot.

We will use emulated Arista vEOS switches in VirtualBox to test our Python apps in a network environment, so you can see the actual results of running your Python code.

I encourage you to learn Python, an amazingly beginner-friendly programming language and take your network engineering job to a higher level of automation.

✔ Is this course regularly updated?

Major Update: December 12th, 2018 – Re-filming the network applications part of the course, upgrading to Python 3.

Major Update: November 8th, 2018 – Re-filmed the first 10 sections of the course, upgraded to Python 3 and improved the video quality to 1080p Full HD.

Course Launch: May 19th, 2015

✔ What others have to say about this course?

“I have been programming since 1978 and wanted to learn python. I have had no java or OOP experience, and I tried several ‘paper’ tutorials but got little out of them. The first part of this course is a steady walk through the Python language at just the right speed. The instructor seems to touch all the basis in a logical and methodical way while providing examples and explanations. I can only conclude the instructor is a professional educator who spent considerable time structuring and organizing the course. The result is evident. THIS IS A GREAT WAY TO LEARN PYTHON!” by Larry Laswell

“I’ve tried learning from the books & multiple videos – most were too basic to make a practical app. Some books were too thick and made me sleep. But still none of the materials had the perfect balance like this course where all the basics were covered, instructions were concise, and Mihai walks you through how to create 7 practical apps step by step. I’ve also tried reading some advanced python book which didn’t make sense because it was too advanced. Let me tell you, this is hands down “that course that takes you up to beyond the basics” to bridge you to the advance topics. Right now I’m hitting the advanced topics and it finally makes sense…” by Joon Park

“Usually I’m not doing courses review but this time I will make an exception. During time I took a lot of trainings but very few provided by Udemy proved as having the right approach in teaching the audience. I will mark this one as being one of my personal top three best trainings as content’s quality, technical explanations, and additional learning materials perspective. Long story short this course is a very simple, straight forward way of learning Python for managing IT networks.” by Johnny Stanescu

“This is a great course for network engineers who would like to start automating their tasks. Geared towards beginners, this course teaches the fundamentals of programming and applying those concepts to networking. There is a lot of fluff about python on the internet, however the instructor managed to put together the necessary information to start automating the network. A working knowledge of TCP/IP is needed to get the most out of this course. Should you understand every lecture, you will be ready to start writing your own scripts according to your needs. In particular, I loved the use of scapy, an amazing tool which should be in the arsenal of anyone working with TCP/IP.” by Costin-Alin Neacsu

“I’ve seen the blueprint and some demo videos and I was convinced right away. Without a doubt, it’s one of the best trainings a network engineer can have. It gives you actual valuable and marketable skills that you can use in your daily job. Mihai explains the topics really well, with practical examples making it a fun way to learn. Highly recommended.” by Vlad Vlaicu

⚠ Important information before you enroll!

In case you find the course useless for your career, don’t forget you are covered by a 30-day money back guarantee, full refund, no questions asked.

Once enrolled, you have unlimited, 24/7, lifetime access to the course (unless you choose to drop the course during the first 30 days).

You will have instant and free access to any updates I’ll add to the course – video lectures, additional resources, exercises or new code.

You will benefit from my full support regarding any question you might have and your course colleagues will help you, as well. This is not just a programming course, it’s an amazing learning community!

Check out the promo video at the top of this page and some of the free preview videos in the curriculum to get a taste of my teaching style and methods before making your decision!

“I would firstly thank you for making this course . Secondly, i did like the approach. You understand the mindset of the beginner. I would recommend this course for all those who want to consider using Python for network automation.” by Pramod Ramu

✔ Enroll NOW and hop on the Python 3 Network Programming train. Let’s get started!

Who this course is for:

Network Administrators, Network Engineers, Network Managers, Systems Engineers.

Network Quality Assurance Engineers, Network Analysts, Network Professionals.

Python Developers Who Want to Apply Their Knowledge in Network Automation.

Created by Mihai Catalin Teodosiu, Python Developer, Python Tutorial I/O Last updated 1/2019 English English [Auto-generated]

Size: 5.38 GB

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