10 ArticlesEvery Programmer Must Read

Being a Java programmer and Software developer, I have learned a lot from articles titled as What Every Programmer Should Know about , they tend to give a lot of useful and in-depth information about a particular topic, which otherwise is very hard to discover. In my quest of learning I have come across some very useful articles, which I have bookmarked for reference and multiple reading. I personally think that all programmer can benefit by reading these articles, which makes me write this post and share all of these "What Every Programmer Should Know" articles with you guys. These are from my personal bookmarks. In this article, you will see classic what every programmer should know article from topics like memory, Unicode, floating point arithmetic, networking, object oriented design, time, URL Encoding, String and many more. This list is very important for beginner and newcomers, as they are the ones, who lacks practical knowledge. Since most of these post are actually driven by practical knowledge, beginner and intermediate programmers can take a lot from it. Also gaining knowledge of fundamentals early in career helps to avoid mistakes, which has done by other programmers and software developers on their course of learning. Though it’s not easy to grasp all knowledge given in these articles in just one reading. You probably won't understand some details about floating point number or get confused with subtle details of memory, but it’s important to keep these list handy and refer them time to time with a context. So Good luck and Enjoy reading these wonderful articles.  By the way, don't forget to share any What Every Programmer Should know article, if it’s not already in this list.


What Every Programmer Should Know about Memory
This is one of the classic article, which will take you through may lanes of memory, some old, some new, some known and some unknown. Despite being so conman and omnipresent, not every programmer have enough knowledge of Memory. Knowledge of memory in modern system becomes even more important if you are in space of writing high performance application. Hardware designers have come up with ever more sophisticated memory handling and acceleration techniques–such as CPU caches–but these cannot work optimally without some help from the programmer. I am still reading this article, and I can't tell you how much I have learned from this about RAM, CPU Caches e.g. L1 and L2 cache, different types of memory, direct memory access, memory controller designs andMemory in general. In short, a must read for programmers of all level of experience.


What Every Computer Scientist Should Know About Floating-Point Arithmetic
Floating point arithmetic is a tricky topic, and it’s not easy to master. Even many Java programmer doesn't know what can go wrong when comparing float/double value with == operator. Many of us often makes mistake of doing monetary calculation in float and double. This article is another gem of this series and must read for all software developers and programmers. As your experience grows, you are expected to know subtle details of common things, and floating point arithmetic is one of them. As as senior Java developer, you must know how do perform monetary calculation, when to use float, double or BigDecimal classes, how to round floating point numbers etc. Even if you know fundamentals of floating point arithmetic, You will learn something new about floating point calculation by reading this article.


What Every Developer Should know about Unicode
Character encoding is another area, where many programmer struggle, and "The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!)" aims to fill that gap. On side note, Yes that's the full title of that article. It was written by Joel Spolsky, one of the founder of statckoverflow.com. Joel has written this post on his blog almost 10 years back, but it is still relevant in today’s world. This article will teach you about What is Unicode, What is character encoding, how characters are represented using bytes and many more. One of the best thing about this article is language and flow, even if you don't know anything about Unicode, you can easily follow. In short, one more must read for all programmers, coders and software engineers.


What Every Programmer Should know about Time
Apart from Character encoding, time and date is another area, where many programmers struggle, including me. Even senior developers lost between GMT, UTC, day light saving and between leap seconds. Frankly speaking, It's not easy to deal with time zones without making any mistake, then add day light savings and effect of that. Problems becomes worse if you using trial and error method, because you will never able to solve your problem by doing that. There are so many things which can go wrong and there are equal number of misconceptions. Things like, whether date contains time-zone or not can confuse you like hell, converting UNIX time to other time-zone can freak you out, forget about clock synchronization and delays. I hope many of your misconception about time will go away and you will build sound fundamental about Time, by reading this classic article.


What every web developer must know about URL encoding
This article describes common misconceptions about Uniform Resource Locator (URL) encoding, then attempts to clarify URL encoding for HTTP, before presenting frequent problems and their solutions. While this article is not specific to any programming language, it illustrate the problems in Java) and finish by explaining how to fix URL encoding problems in Java, and in a web application at several levels. You will learn basics of URL grammar, general URL syntax in HTTP and other protocol. This article also explores common pitfalls of URLs e.g. character encoding, reserved character at different part of URL, and URL encoding/decoding issues. If you are a Java programmer, then you will also learn about how to handle URLs in Java application, the right way. How to construct URL and using Apache commons HTTP client library. Finally it also suggest best practices or dealing with URLs e.g. you should encode URLs when you build them, making sure your URL-rewrite filters deal with your URL correctly and many more. In short, a must read article for any web developer and programmer.



What should every programmer know about web development?
This is an interesting article from programmers stack exchange, about what should every programmer implementing the technical details of a web application consider before making the site public. This includes things ranging from Interface design and User Experience, Security, Web standards, Performance, Search Engine Optimization(SEO), Technology involved, and about several important resources. Since today's world is hugely dependent upon internet and programmer having their personal site, blog is quite common. Experience learned on this article will not even help in your professional work but also in your personal work. You will learn about all key technology e.g. HTTP, HTML, XML, CSS, JavaScript, browsers compatibility, tips to reduce loading time of your website, XML sitemaps, W3C specifications and several other key details.


What Every Programmer Should Know About SEO
This is another article, which is very important for web developers, programmers and blogger. SEO is too big to ignore, since many programmers are also blogger, it’s important to learn few basics of Search Engine Optimization to help Google find their content and present to other fellow programmers. Since no company can survive without web presence in today's inter-connected world, SEO becomes even more important. If you own start-up, selling any product, then SEO is something to care about. All programmers, especially web developers can largely benefit from this article. Remember, Search Engine Optimization is vast and very dynamic subject, and also varies between different search engines e.g. Google, Yahoo, and others. So, In order to master this topic you will always need to update your knowledge.


What Every C Programmer Should Know About Undefined Behaviour #1/3
C programming language have the concept of "undefined behaviour". Undefined behaviour is a broad topic with a lot of nuances and that's one reason of Why I like Java, less number of undefined behaviour, less confusion, more stability and more peace. Many seemingly reasonable things in C actually have undefined behaviour, and this is a common source of bugs in programs. Beyond that, any undefined behaviour in C gives license to the implementation (the compiler and runtime) to produce code that formats your hard drive, does completely unexpected things, or worse. Read this excellent article to deep dive on sea of undefined behaviour


What Every Programmer Need to know about networking
From the article itself "You’re a programmer. Have you ever wondered how multi-player games work? From the outside it seems magical: two or more players sharing a consistent experience across the network like they actually exist together in the same virtual world. But as programmers we know the truth of what is actually going on underneath is quite different from what you see. It turns out that it’s all an illusion." This is very interesting article about networking, written for game programmers but I think every programmer and developer can benefit from this.


What Every Java Developer Should Know about String
This is my article on java.lang.String and what I personally thing every Java programmer should know about it. String is very important in day to day programming in Java and that's why good knowledge is must for any Java developer. This article touches many important areas of String including string pool, string literal, comparing String using == vs equals(), converting bytes to String, Why String is immutable, properly concatenating Strings and many more. Advanced programmer may already know all these stuffs but even then it’s good to revise them.


What should every programmer know about security?
This question was ask by one computer programming student in StackOverFlow. Just like we learn a lot about general programming concepts e.g. operating system, algorithm, data-structure, computer architecture, and other stuff, its also important to know about security. Though Security is vast topic ranging from encryption/decryption, SSL, web security, obfuscation, authentication, authorization etc, a basic minimum knowledge is must for every programmer. I personally didn't know much about Security when I started my career, its when I start writing Servlet/JSP based Java web application, I come to know about web security and several security threats like SQL Injection, Denial of Service, XML Injection, Cross site scripting and others. As Java developer, now I follow secure Java coding practices provided by fortify, PMP and other static code analysis providers.  This article is very good collection of topics and links about Security and whether you are doing coding or not, you will surely benefit from this resource.


Latency Numbers Every Programmer Should Know
This is the bonus article, but must read for every Programmer. In order to write high performance application in any programming language e.g. Java or C++, you ought to know fundamental latency numbers e.g. how much time it take to read a variable from memory, from L1 Cache, from L2 cache, from random read in SSD and from disk. How much time it take to lock unlock on mutex, to send a data packet from one city to another or doing a roundtrip on same data centre. These latency numbers are independent of any programming language and part of core knowledge, a developer must have to write high frequency low latency applications. Good thing about this link is that it also provides you comparative analysis of how these latency numbers have evolved over the years. You can see what these latency numbers were in 2006 and what they are now.


That's all in this list of article every Programmer must read. By reading articles titles as What Every Programmer or Developer Should know, you gain in-depth knowledge of a particular topic. Frankly speaking there are too many things to learn for programmers, learning a programming language like Java is just a tip of iceberg, but isn't it many of us have passion for learning. Programming is a challenging job, and only things which help you all along your career is fundamental knowledge e.g. things about Memory, Unicode, floating point numbers, time, security is very important for any programmer. Few things are programming language specific e.g. my post about Java String and What every C programmer should know about undefined behaviour, but they are still good to learn for many beginner and developers.

10 Object Oriented Design Principles Java Programmer should know

Object Oriented Design Principles are core of OOPS programming, but I have seen most of Java programmer chasing design patterns like Singleton pattern , Decorator pattern or Observer pattern , and not putting enough attention on learning Object oriented analysis and design. It's important to learn basics of Object oriented programming like Abstraction, Encapsulation, Polymorphism and Inheritance, but same time, it's equally important to know these design principles, to create clean and modular design. I have regularly seen Java programmers and developers of various experience level, who either doesn't heard about these OOPS and SOLID design principle, or simply doesn't know what benefits a particular design principle offers, or how to use these design principle in coding.

Bottom line is, always strive for highly cohesive and loosely couple solution, code or design. Looking open source code from Apache and Sun are good examples of learning Java and OOPS design principles. They show us,  how design principles should be used in coding and Java programs. Java Development Kit follows several design principle like Factory Pattern in BorderFactory class,  Singleton pattern in Runtime class,Decorator pattern on various java.io classes. By the way if you really interested more on Java coding practices,  read Effective Java by Joshua Bloch , a gem by the guy who wrote Java API. My another personal favorite on object oriented design pattern is,  Head First Design Pattern by Kathy Sierra and others and Head First Object Oriented Analysis and Design . These books helps a lot to write better code, taking full advantage of various Object oriented and SOLID design principles.

Though best way of learning any design principle or pattern is real world example and understanding the consequences of violating that design principle, subject of this article is Introducing Object oriented design principles for Java Programmers, who are either not exposed to it or in learning phase. I personally think each of these OOPS and SOLID design principle need an article to explain them clearly, and I will definitely try to do that here, but for now just get yourself ready for quick bike ride on design principle town :)

DRY (Don't repeat yourself)

Our first object oriented design principle is DRY, as name suggest DRY (don't repeat yourself) means don't write duplicate code, instead use Abstraction to abstract common things in one place. If you have block of code in more than two place consider making it a separate method, or if you use a hard-coded value more than one time make them public final constant. Benefit of this Object oriented design principle is in maintenance. It's important  not to abuse it, duplication is not for code, but for functionality . It means, if you used common code to validate OrderID and SSN it doesn’t mean they are same or they will remain same in future. By using common code for two different functionality or thing you closely couple them forever and when your OrderID changes its format , your SSN validation code will break. So beware of such coupling and just don’t combine anything which uses similar code but are not related.

Encapsulate What Changes

Only one thing is constant in software field and that is "Change", So encapsulate the code you expect or suspect to be changed in future. Benefit of this OOPS Design principle is that Its easy to test and maintain proper encapsulated code. If you are coding in Java then follow principle of making variable and methods private by default and increasing access step by step e.g. from private to protected and not public. Several of design pattern in Java uses Encapsulation, Factory design pattern is one example of Encapsulation which encapsulate object creation code and provides flexibility to introduce new product later with no impact on existing code.

Open Closed Design Principle

Classes, methods or functions should be Open for extension (new functionality) and Closed for modification. This is another beautiful SOLID design principle, which prevents some-one from changing already tried and tested code. Ideally if you are adding new functionality only than your code should be tested and that's the goal of Open Closed Design principle. By the way, Open Closed principle is "O" from SOLID acronym.

Single Responsibility Principle (SRP)

Single Responsibility Principle is another SOLID design principle, and represent  "S" on SOLID acronym. As per SRP, there should not be more than one reason for a class to change, or a class should always handle single functionality. If you put more than one functionality in one Class in Java  it introduce coupling between two functionality and even if you change one functionality there is chance you broke coupled functionality,  which require another round of testing to avoid any surprise on production environment.

Dependency Injection or Inversion principle

Don't ask for dependency it will be provided to you by framework. This has been very well implemented in Spring framework, beauty of this design principle is that any class which is injected by DI framework is easy to test with mock object and easier to maintain because object creation code is centralized in framework and client code is not littered with that.There are multiple ways to  implemented Dependency injection like using  byte code instrumentation which some AOP (Aspect Oriented programming) framework like AspectJ does or by using proxies just like used in Spring. See this example of IOC and DI design pattern to learn more about this SOLID design principle. It represent "D" on SOLID acronym.

Favor Composition over Inheritance

Always favor composition over inheritance ,if possible. Some of you may argue this, but I found that Composition is lot more flexible than Inheritance. Composition allows to change behavior of a class at runtime by setting property during runtime and by using Interfaces to compose a class we use polymorphism which provides flexibility of to replace with better implementation any time. Even Effective Java advise to favor composition over inheritance.

Liskov Substitution Principle (LSP)

According to Liskov Substitution Principle, Subtypes must be substitutable for super type i.e. methods or functions which uses super class type must be able to work with object of sub class without any issue". LSP is closely related to Single responsibility principle and Interface Segregation Principle. If a class has more functionality than subclass might not support some of the functionality ,and does violated LSP. In order to follow LSP SOLID design principle, derived class or sub class must enhance functionality, but not reduce them. LSP represent  "L" on SOLID acronym.

Interface Segregation principle (ISP)

Interface Segregation Principle stats that, a client should not implement an interface, if it doesn't use that. This happens mostly when one interface contains more than one functionality, and client only need one functionality and not other.Interface design is tricky job because once you release your interface you can not change it without breaking all implementation. Another benefit of this design principle in Java is, interface has disadvantage to implement all method before any class can use it so having single functionality means less method to implement.

Programming for Interface not implementation

Always program for interface and not for implementation this will lead to flexible code which can work with any new implementation of interface. So use interface type on variables, return types of method or argument type of methods in Java. This has been advised by many Java programmer including in Effective Java and head first design pattern book.

Delegation principle

Don't do all stuff  by yourself,  delegate it to respective class. Classical example of delegation design principle is equals() and hashCode() method in Java. In order to compare two object for equality we ask class itself to do comparison instead of Client class doing that check. Benefit of this design principle is no duplication of code and pretty easy to modify behavior.

All these object oriented design principle helps you write flexible and better code by striving high cohesion and low coupling. Theory is first step, but what is most important is to develop ability to find out when to apply these design principle. Find out, whether we are violating any design principle and compromising flexibility of code, but again as nothing is perfect in this world, don't always try to solve problem with design patterns and design principle they are mostly for large enterprise project which has longer maintenance cycle.