Showing posts with label best practices. Show all posts
Showing posts with label best practices. Show all posts

Spring Framework Java Tips and Best practices to avoid NullPointerException in Java Applications

A NullPointerException in Java application is best way to solve it and that is also key to write robust programs which can work smoothly. As it said “prevention is better than cure”, same is true with nasty NullPointerException. Thankfully by applying some defensive coding techniques and following contract between multiple part of application, you can avoid NullPointerException in Java to a good extent. By the way this is the second post on NullPointerException in Javarevisited, In last post we have discussed about common cause of NullPointerException in Java and in this tutorial,  we will learn some Java coding techniques and best practices, which can be used to avoid NullPointerException in Java. Following these Java tips also minimize number of !=null check, which litter lot of Java code. As an experience Java programmer, you may be aware of some of these techniques and already following it in your project, but for freshers and intermediate developers, this can be good learning. By the way, if you know any other Java tips to avoid NullPointerException and reduce null checks in Java, then please share with us.
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Spring Hibernate Top 10 JDBC Best Practices for Java Programmer

Java JDBC Best practices
JDBC Best Practices are some coding practices which Java programmer should follow while writing JDBC code. As discussed in how to connect to Oracle database from Java, JDBC API is used to connect and interact with a Database management System.  We have touched some of the JDBC best practices in our last article 4 JDBC Performance tips, On which we have discussed simple tips to improve performance of Java application with database. By using JDBC you can execute DDL, DML and Stored Procedures. JDBC Best practices is probably most significant set of coding practices in Java because it significantly affect performance of Java application. I have seen substantial performance gain by simply following common JDBC best practices like running queries with auto commit mode disable. One of the query which we used in our example of JDBC Batch update was taking almost 30 second to finish with auto commit mode enabled but it just took under one second with auto commit mode disable and using explicit commit. This JDBC tutorial is collection of such practices which help you to write better JDBC code and in most cases result in improved performance.
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Spring Framework 10 Exception handling Best Practices in Java Programming

Exception handling is an important part of writing robust Java application. It’s a non functional requirement for any application, to gracefully handle any erroneous condition like resource not available, invalid input, null input and so on. Java provides several exception handling features, in built in language itself in form of try, catch and finally keyword.  Java  programming language also allows you to create new exceptions and throw them using  throw and throws keyword. In reality, Exception handling is more than knowing syntax. Writing a robust code is an art more than science, and here we will discuss few Java best practices related to Exception handling. These Java best practices are followed even in standard JDK libraries, and several open source code to better deal with Errors and Exceptions. This also comes as handy guide of writing robust code for Java programmers.
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Java J2EE Spring 10 Best Practices to Follow while writing Code Comments

Comments are an important part of writing code not only in Java, but whatever programming or scripting language you use. At the same time this is one of the most abused things as well. Both writing no comment and writing too much comment is bad and this has been high lighted by many software gurus e.g. Robert C. Martin in his classic book Clean code. There is a whole chapter dedicated on How to write comments and finding pros and cos of comment. This article is my learning in same direction, here I am going to share with you guys some 0f the rule and best practices I follow while writing comments. Before that let's first see what is the purpose of having comment in the code? Why do we need comment, isn't writing code is enough. Some of the people I have met always argue that we are getting paid for writing code and not comment :).

code comments best practices in javaAnyway in my opinion we all agree with each other that software spend only 10% time of its life in development and rest of 90% in maintenance. This 90% part of maintaining the code is where comment can help you immensely. Since no single developer stays till whole life of any product or software and its often new people, who works of already written code. These are the people who read the code and not aware of why a certain piece of code has been written, here comments can help them to understand code quickly and believe me you will get lot of roses from that fellow developer :). 

Anyway long story short here are some of the things I try to follow while writing code:

10 tips on writing code comments

1) Focus on readability of code; assume that you don't have comments to explain the code. Give your method, variables and class meaningful name.

2) Don't write what code is doing, this should be left for the code to explain and can be easily done by giving class, variable and method meaningful name. For example:

//calculates square root of given number 
//using Newton-Raphson method
public void abc(int a){
       r = a / 2;
       while ( abs( r - (a/r) ) > t ) {
       r = 0.5 * ( r + (a/r) );
       }
       System.out.println( "r = " + r );
}
 
Above code is calculating square root using Newton-Raphson method and instead of writing comment you can just rename your method and variable as follows:

public void squareRoot(int num){
       root = num/ 2;
       while ( abs(root - (num/ root) ) > t ) {
       r = 0.5 * (root + (num/ root));
       }
       System.out.println( " root = " + root );
}
 
3) Always write why you are writing this piece of code, why you are writing this piece of code because this information is not visible until you write them in comments and this is critical to identify any bug or behavior with changing business environment.

4) If you are writing core libraries which will be used by different project and with different teams. Follow javadoc comment style and document all assumption and precondition for using your API. Joshua Bloch has also mentioned about writing Java-doc comment in his classic Effective Java, which is worth knowing.

5) Include JIRA Number and description on comment, especially if you are modifying an existing piece of code as part of maintenance. This I found extremely useful while comparing different version of code in CVS or SVN. This gives you clear idea why that particular code has been added and whether issue is because of that piece of code or not.


6) Always try to finish your comment in as few words as possible, one liner comment is best until its explaining "Why" part and can't be replaced by code itself. No body likes or has enough time to read longer comment.

7) Don't write story in comment as your name, employee id, your department etc because those information can be obtained from CVS commit data in case someone wants to know who has make this change.

8) Always put comment while committing code in source control repository and especially why you are adding this piece of code if possible include JIRA or QC Number so that any one can refer JIRA for complete details.

9) If you want upcoming developer to follow certain standards or inform about certain things then include them in the beginning of your class as comment. E.g. suppose if you are writing serializable class in java then its good to put a serializable alert stating that any new fields addition in this class must implement serializable interface in java or make it transient etc.


10) Last but not the least give your code to fellow developer to understand as part of code review and ask him how much he understands it.

That’s all from me on code commenting, please share the standard, best practices or your experience with writing comments on code. I believe these are the areas which a junior developer or even we can improve and it’s only possible from learning which each mother's experience.
Happy weekend :)

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Why wait and notify method must be called in synchronized context?
10 practical tips on Java debugging with eclipse
How Synchronization works in Java?
How Classpath works in Java?
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Spring Framework Java Best Practices to Follow while Overloading Method and Constructor

Method overloading in Java needs to be use carefully. Poorly overloaded method add not only add confusions among developers who use that but also they are error prone and leaves your program on compiler's mercy to select proper method. It's best to avoid issues related to method overloading in Java by following some Java best practices. For those who doesn’t know What is method overloading in Java, method overloading means declaring two method with same name but different method signatures. This is generally done to create method which operates on different data types e.g. System.out.println() which is overloaded to accept different types of parameters like String, double, int etc, see this Java tutorial on method overloading and static vs dynamic binding for more details. By the way all of these Java best practices which are explained in context of method overloading are equally applicable to constructor overloading in Java, because in terms of overloading method and constructors are almost same.
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Spring Framework Java Mistake 3 - Using "==" instead of equals() to compare Objects in Java

In this part of Java programming mistakes, we will take a look on another common pattern, where programmers tend to use "==" operator to compare Objects, similar to comparing primitives. Since equality of object can be very different in physical and logical sense, and in case of domain objects it's mostly driven by business rules, comparing objects with "==" operator, introduces subtle bugs, which are hard to find. Difference between equals() and == operator,  one of the Java classics is also asked to find out if developer is familiar with this important concept or not. Using == operator only make sense when comparing primitives like int, or final constants like Enum. Though there is more involve in comparing two Enum, which you learn by following that link. One of the most common pattern of this mistake is is comparing two Strings with == operator, which we will see in this article. By the way this is third in series of common Java programming mistakes, and if you haven't read the previous two, you can read them here :
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Spring Framework Why Favor Composition over Inheritance in Java and Object Oriented Programming

Favor composition over inheritance is a one of the popular object oriented design principle, which helps to create flexible and maintainable code in Java and other object oriented languages. Many times I have seen people suggesting use composition instead of inheritance, in fact my favorite books like Head first Design Patterns, also advocates this design principle. Head first books, has its own way of explaining, why composition is better than inheritance and though its long its quite interesting and informative. It was the first chapter of this book, which helped me a lot on understanding this key OOPS concept. In this Java and OOPS tutorial, I have tried to summarize my experience around composition and inheritance in two main category, first, difference between composition and inheritance and second, when to use Composition over inheritance in Java. I have already mentioned about this design principle, in my list of 10 OOPS and SOLID design principles for Java programmers, here we will take a more closer look.
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Spring Framework Why getter and setter are better than public fields in Java

public modifier vs getter and setter method in Java
Providing getter and setter method for accessing any field of class in Java may look unnecessary and trivial at first place, simply because you can make field publicand it’s accessible from everywhere in Java program. In fact many programmers do this in there early days but once you start thinking in terms of enterprise application or production code, you will start seeing how much trouble it can create in terms of maintenance. Since as per SDLC process, software spends more time in maintenance than development, it’s worth keeping ease of maintenance as one of goal in development. In reality using getter and setter method in Java is one of the Java coding best practice much like using @Override annotation while overriding method in Java. Main problem with making field public instead of getter and setter is that it violates Encapsulationby exposing internals of a class. Once you exposed internals of class  you can not change internal representation or make it better until making change in all client code. Since every code change comes with risk and cost of regression testing is high during maintenance, its not a good idea to make field public in Java.  In this Java tutorial we will see some more benefits getter and setter offers over public fields in Java.
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Spring Framework How to create Immutable Class and Object in Java - Tutorial Example

Writing or creating immutable classes in Java is becoming popular day by day, because of concurrency and multithreading advantage provided by immutable objects. Immutable objects offers several benefits over conventional mutable object, especially while creating concurrent Java application. Immutable object not only guarantees safe publication of object’s state, but also can be shared among other threads without any external synchronization. In fact JDK itself contains several immutable classes like String, Integer and other wrapper classes. For those, who doesn’t know what is immutable class or object, Immutable objects are those, whose state can not be changed once created e.g. java.lang.String, once created can not be modified e.g. trim, uppercase, lowercase. All modification in String result in new object, see why String is immutable in Javafor more details. In this Java programming tutorial, we will learn, how to write immutable class in Java or how to make a class immutable. By the way making a class immutable is not difficult on code level, but its the decision to make, which class mutable or immutable which makes difference. I also suggest reading, Java Concurrency in Practiceto learn more about concurrency benefit offered by Immutable object.
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Spring Framework Why use @Override annotation in Java - Coding Best Practice

@Override annotation was added in JDK 1.5 and it is used to instruct compiler that method annotated with @Override 
is an overridden method from super classor interface. Though it may look trivial @Override is particularly useful while
overriding methods which accept Object as parameter just like equals, compareToor compare() method of Comparator 
interface. @Override is one of the three built in annotation provided by Java 1.5, other two are @SuppressWarnings and @Deprecated. Out of these three @Override is most used because of its general nature, while @SuppressWarnings is also used while using Generics, @Deprecated is mostly for API and library. If you have read my article common errors while overriding equals method than you have see that one of the mistake Java programmer makes it,  write equals method with non object argument type as shown in below example:
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