Tuesday 24 November 2015

Github

https://github.com/about

To understand GitHub, you must first have an understanding of Git. Git is an open-source version control system that was started by Linus Trovalds – the same person who created Linux. Git is similar to other version control systems – Subversion, CVS, and Mercurial to name a few.

http://www.howtogeek.com/180167/htg-explains-what-is-github-and-what-do-geeks-use-it-for/

http://techcrunch.com/2012/07/14/what-exactly-is-github-anyway/

What is the difference between Git and GitHub?

Git is a version control system; think of it as a series of snapshots (commits) of your code. You see a path of these snapshots, in which order they where created. You can make branches to experiment and come back to snapshots you took.

GitHub, is a web-page on which you can publish your Git repositories and collaborate with other people.
Is Git saving every repository locally (in the user's machine) and in GitHub?

No, it's only local. You can decide to push (publish) some branches on GitHub.
Can you use Git without GitHub? If yes, what would be the benefit for using GitHub?

Yes, Git runs local if you don't use GitHub. An alternative to using GitHub could be running Git on files hosted on Dropbox, but GitHub is a more streamlined service as it was made especially for Git.
How does Git compare to a backup system such as Time Machine?

It's a different thing, Git lets you track changes and your development process. If you use Git with GitHub, it becomes effectively a backup. However usually you would not push all the time to GitHub, at which point you do not have a full backup if things go wrong. I use git in a folder that is synchronized with Dropbox.
Is this a manual process, in other words if you don't commit you won't have a new version of the changes made?

Yes, committing and pushing are both manual.
If are not collaborating and you are already using a backup system why would you use Git?

If you encounter an error between commits you can use the command git diff to see the differences between the current code and the last working commit, helping you to locate your error.
You can also just go back to the last working commit.
If you want to try a change, but are not sure that it will work. You create a branch to test you code change. If it works fine, you merge it to the main branch. If it does not you just throw the branch away and go back to the main branch.
You did some debugging. Before you commit you always look at the changes from the last commit. You see your debug print statement that you forgot to delete.
Reference:-

http://stackoverflow.com/questions/11816424/understanding-the-basics-of-git-and-github

Monday 2 November 2015

Best of Eclipse

How to do static import in Eclipse - Java

Do you know what is shortcut of doing static import in Eclipse? Well I didn't know before, but today I come to know that shortcut Ctrl+Shift+M (Source > Add Import) can not only be used to add missing...

Jar Artifiact Dependency Search Not Working in Eclipse - Solved

Recently I face an strange issue while using Maven in Eclipse via M2Eclipse plugin. I have created a Maven Java project in Eclipse and subsequently tried to add Spring framework as dependency, to my...

How to See difference between two Files in Eclipse - Text Comparision

One of the common task for every programmer is is to compare two files and find out difference between them. You would do this while comparing same file from different release version or from different...

Eclipse Not Able To Connect Internet, Market Place - Configure Connection Proxy Settings

If you are using Eclipse in your company, you might have faced issues, where Eclipse is not able to connect to internet. Since most of companies uses proxy for connecting to Internet, its important to...

Eclipse No Java Virtual Machine was found Windows JRE JDK 64 32 bit Error

One of my reader was installing Eclipse in his Windows 7 x86 machine and emailed me about this error "A java Runtime Environment (JRE) or Java Development kit (JDK) must be available in order to run...

What is java.library.path , How to set in Eclipse IDE

java.library.path is a System property, which is used by Java programming language, mostly JVM, to search native libraries, required by project. Similar to PATH and Classpath environment variable, java.library.path...

How to Increase Console Buffer Size in Eclipse IDE - Output and Debug Console

By default Eclipse IDE has limit on console output, also known as console buffer size. Which means, your Eclipse console will overfill quickly, if you are running a Java server program, which usually...

How to Fix Must Override a Superclass Method Error Eclipse IDE Java | @Override annotation With interface methods

One of annoying error while overriding Java method in Eclipse IDE is must override a superclass method error , This error is quite frequent when importing Java projects and still I haven't seen...

How to fix Failed to load Main-Class manifest attribute from jar - Java Eclipse Netbeans Tutorial

If you have tried creating JAR file and running Java program form command line you may have encountered "Failed to load Main-Class manifest attribute from jar" , This error which haunts many Java programmer...

How to decompile class file in Java and Eclipse - Javap command example

Ability to decompile a Java class file is quite helpful for any Java developer who wants to look into the source of any open source or propriety library used in project. Though I always prefer to attach...

How to attach source in eclipse for Jars, debugging and code look-up – JDK Example

Attaching source of any Jar in Eclipse e.g. JDK or open source libraries like Spring framework is good idea because it help during debugging and code development. As a Java programmer at least you should...

How to escape String literal in Java using Eclipse IDE

Whenever you paste String in Eclipse which contains escape characters, to store in a String variable or just as String literal it will ask to manually escape special characters like single quotes,...

How to comment uncomment single line and block of code in Java - Eclipse Tips Tricks

Knowing Eclipse shortcut to comment and uncomment single line or block of code can save you lot of time while working in Eclipse. In fact I highly recommend every Java programmer to go through these...

Eclipse shortcut to System.out.println in Java program - Tips

Eclipse IDE provides quick shortcut keys to print System.out.println statement in Java but unfortunately not every Java programmers are familiar of that. Even programmers with 3 to 4 year of experience...

Eclipse shortcut to remove all unused imports in Java file

How to remove all unused imports in Eclipse Eclipse IDE gives warning "The import XXX is never used" whenever it detect unused import in Java source file and shows a yellow underline. Though unused...

Finally Eclipse supports JDK7 in Eclipse Indigo 3.7.1

Much awaited release of Eclipse with JDK7 is now over, Eclipse has announce release of version Indigo 3.7.1 which will support JDK7.though I already have downloaded Netbeans with JDK7 support I was...

10 Tips to Debug Java Program in Eclipse

How to debug java program in Eclipse Debugging is a must have skill for any java developer. Having ability to debug java program enables to find you any subtle bug which is not visible during code...

How to setup Java remote debugging in Eclipse

How to remote debug Java program in Eclipse Remote debugging is not a new concept and many of you are aware of this just for who don’t know what is remote debugging? It’s a way of debugging any process...

Top 30 Eclipse Keyboard Shortcuts for Java Programmer

This tutorial is about 30 Eclipse keyboard shortcuts, this list is by no means complete and I will suggest you guys to share eclipse shortcuts listed other than here to make this more useful. Eclipse...

Tuesday 29 September 2015

Top 30 Eclipse Keyboard Shortcuts for Java Programme

This tutorial is about 30 Eclipse keyboard shortcuts, this list is by no means complete and I will suggest you guys to share eclipse shortcuts listed other than here to make this more useful.Eclipse is most used Java development IDE and knowing Eclipse shortcuts not only improve your productivity but also makes you more efficient, you will have more time for things you like to do. Using keyboard shortcuts also helps to impress colleagues and shows that you have good hold on tools you used for Java Development.

I was big fan of Netbeans IDE before coming across Eclipse because I was from J2ME background and Netbeans provide sophisticated IDE environment to enable you to build, debug and run your Java application in various emulator including some advanced processing options e.g. preprocessing, setting up Exception break-point etc. From that time I love to know keyboard shortcuts on IDE and other tools I used for development including Edit Plus, Microsoft Excel etc.

But when I join an investment bank I came across Eclipse IDE, since everybody in my team is using and Netbeans IDE was not available in company (don’t know why that was not allowed net-beans even though it was free) I have decided to go Eclipse way, later I found that Eclipse was most suited for those application given some of cool feature of eclipse e.g. Remote Debugging, Conditional Breakpoints, Exception breakpoints and Ctrl+T and Ctrl+R kind of shortcuts.

Here I am sharing list of 30 Eclipse keyboard shortcuts which I found most useful and using in my day to day life while writing code, reading code or debugging Java application in Eclipse.

Eclipse Keyboard Shortcuts

1) Ctrl + T for finding class even from jar

This keyboard shortcut in Eclipse is my most used and favorite shortcut. While working with high speed trading system which has complex code I often need to find classes with just blink of eye and this eclipse keyboard shortcut is just made for that. No matter whether you have class in your application or inside any JAR, this shortcut will find it.

2) Ctrl + R for finding any resource (file) including config xml files

This is similar to above Eclipse shortcut with only difference that it can find out not only Java files but any files including xml, configs and many others, but this eclipse shortcut only finds files from your workspace and doesn’t dig at jar level.

3) Ctrl + 1 for quick fix

This is another beautiful Eclipse shortcut which can fix up any error for you in Eclipse. Whether it’s missing declaration, missing semi colon or any import related error this eclipse shortcut will help you to quickly short that out.

4) Ctrl + Shift + o for organize imports

Another Eclipse keyboard shortcut for fixing missing imports. Particularly helpful if you copy some code from other file and what to import all dependencies.

Eclipse Shortcut for Quick Navigation

In this section we will see some eclipse keyboard shortcut which helps to quickly navigate within file and between file while reading and writing code in Eclipse.

7) Ctrl + o for quick outline going quickly to method

9) Alt + right and Alt + left for going back and forth while editing.

12) Alt + Shift + W for show in package explorer

13) Ctrl + Shift + Up and down for navigating from member to member (variables and methods)

15) Ctrl + k and Ctrl + Shift +K for find next/previous

24) Go to a type declaration: F3, This Eclipse shortcut is very useful to see function definition very quickly.

Eclipse Shortcut for Editing Code

These Eclipse shortcuts are very helpful for editing code in Eclipse.

5) Ctrl + / for commenting, un commenting lines and blocks

6) Ctrl + Shift + / for commenting, un commenting lines with block comment

8) Selecting class and pressing F4 to see its Type hierarchy

10) Ctrl + F4 or Ctrl + w for closing current file

11) Ctrl+Shirt+W for closing all files.

14) Ctrl + l go to line

16) Select text and press Ctrl + Shift + F for formatting.

17) Ctrl + F for find, find/replace

18) Ctrl + D to delete a line

19) Ctrl + Q for going to last edited place

Miscellaneous Eclipse Shortcuts

These are different Eclipse keyboard shortcuts which doesn’t fit on any category but quite helpful and make life very easy while working in Eclipse.

20) Ctrl + T for toggling between super type and subtype

21) Go to other open editors: Ctrl + E.

22) Move to one problem (i.e.: error, warning) to the next (or previous) in a file: Ctrl +. For next, and Ctrl +, for previous problem

23) Hop back and forth through the files you have visited: Alt + ← and Alt + →, respectively.

25) CTRL+Shift+G, which searches the workspace for references to the selected method or variable

26) Ctrl+Shift+L to view listing for all Eclipse keyboard shortcuts.

27) Alt + Shift + j to add javadoc at any place in java source file.

28) CTRL+SHIFT+P to find closing brace. Place the cursor at opening brace and use this.

29) Alt+Shift+X, Q to run Ant build file using keyboard shortcuts in Eclipse.

30) Ctrl + Shift +F for Autoformating.

Please post if you guys have some more useful Eclipse keyboard shortcuts as comments, I will include them in this list. These Eclipse shortcuts will mostly work almost all Eclipse versions e.g. 3.5, 3.6 Helios, Eclipse Ganymede and Indigo. Let me know if you face any issue while using these Eclipse shortcuts in any particular version of Eclipse IDE.

Monday 21 September 2015

OCAJP 7 or OCAJP 8? Which Java Certification should I take?

Java certification is great way to learn and master The Java programming language, do well on interview and get recognition in job, but most common reason of doing Java certification is to find a job. After Oracle's acquisition and dividing old SCJP exam into two exams OCAJP and OCPJP, it has become really confusing for many developers to decide which Java certification exam they should take. Since technologies change fast and Java is no exception, its just an year when Java 8 was released and now people are talking about Java 9. In general, it is better to go with the latest version of a certification, which is currently available i.e. the Java 8 version. But in case of Java certifications, it's not that simple. Many of my reader email me about my advice to decide between Java SE 6, 7 and 8 exams before zeroing one. After answering their emails, I realize its better to jolt down important points for everyone's benefit. Here are things you should consider before buying Java certification voucher and starting your preparation.

Important points about Java Certifications

The most important thing to know is that from Java 7 onward, Oracle has split the Java Professional certification into two exams - Java Associate level and Professional level. To be a Java 7 or Java 8 certified professional, you need to first pass OCAJP before taking OCPJP, but if you hold any Java certification, you can also take an upgrade exam for Java SE 7 or 8.

If you want to become Java certified developer by giving just one exam, then your only option is to take 1Z0-851 or OCPJP6. It is actually similar to older one SCJP6 and does not require any prior certification.

To acquire the latest Java 8 Professional Certification (OCPJP8), you need to first pass the Java 8 Associate Certification (OCAJP8). In other words you have to take two exams - 1Z0-808 and 1Z0-809. OCAJP 8 is now out of beta and available as normal exam, but OCJPJP 8 (1Z0-809) is not yet released. So even if you pass associate level Java 8 exam now, you need to wait until 1Z0-809 is released. I highly recommend this exam to new developers who are trying to get Java certification, because Java 8 has introduced several new features in language and will provide competitive advantage to you on Interviews. It's also better to learn the future way of using Java sooner than later.

Things are little better for already certified Java developers. Oracle provides upgrade exams for them so that you can update your knowledge and certification to newer version of Java. Since Java 8 is a major release and in coming days will be sought after skill, its better for Java guys to take an appropriate upgrade exam such as 1Z0-810 for Java 8 Professional. For those, who wants to upgrade to Java 7 certification, they can take 1Z0-805 exam.

If you are giving Java certification to get a Job or improve your chances over other candidates then its important to have a certification under your belt, even if its not the latest one. Many developers make mistake of going after OCPJP6 in order to get certify in one attempt but its a difficult exam to crack, especially compared to OCAJP7. It's one of the toughest Java certification out there and many experienced developer was not able to clear it one shot. I don't recommend this to freshers and junior Java developers who are looking for job. Beginners and freshers are better off with preparing OCAJP7 because then the will at-least have one Java certification, which might help them to land a job. Never underestimate power of Java certification, there are many Java job position where consultants are only looking for Oracle certified Java developer.

That's all about which Java certification exam should you take. In short, if you are beginner looking for job then take OCAJP7, if you are a working Java developer then take OCAJP8 and if you are already certified Java developer looking to upgrade to Java 8 then take 1Z0-810. This is also a good time to get Java certified because Oracle is offering 20% discount on all Java exams.

Recommend resources to prepare for Java certification :

OCA and OCP Java SE 7 Programmer I & II Study Guide (Exams 1Z0-803 & 1Z0-804) [see here]
Oracle Certified Professional Java SE 7 Programmer Exams 1Z0-804 and 1Z0-805: A Comprehensive OCPJP 7 Certification Guide By S G Ganesh and Tushar Sharma [see here]
OCA: Oracle Certified Associate Java SE 8 Programmer I Study Guide: Exam 1Z0-808 1st Edition by Jeanne Boyarsky (Author), Scott Selikoff (Author) [see here]

Tuesday 11 August 2015

What is JSR and what's its use?

JSRs are Java Specification Requests, basically change requests for the Java language, libraries and other components.

It's all part of the Java Community Process, whereby interested parties can put forward their ideas for enhancements and (hopefully) have them taken up and acted upon. The process is detailed here.

For example, the Bluetooth one you mention is tracked here and the definitive list is maintained here.

ref:-

http://stackoverflow.com/questions/9901976/what-is-jsr-and-whats-its-use

Sunday 2 August 2015

What is the Jenkins and Maven difference

Maven-build tool Jenkins-CI tool. you can read more about Jenkins here:- https://en.wikipedia.org/wiki/Jenkins_(software) it's stackoverflow difference here:- --------------------------------------------------------------- Maven is building tool/environment. Jenkins, on the other hand, is a CI (continuous integration) tool. Maven is more like a replacement for Ant. It gives basic support for build and version control, JUnit tests, etc... you define what you want to do in a pom.xml file. Jenkins itself doen't support build / version control or JUnit, but rather it calls the pom.xml file you have defined in your project. Jenkins gives you the power to decide when to call the pom.xml file, how to call, and what you want to do with the outcome. This is a powerful idea. For example, you can ask Jenkins to trigger a build or run through all JUnit tests whenever new code is committed and then, if the unit tests are passed, deploy on a target machine. This is the basic idea of auto deployment or AKA continuous integration. CI for short if you like. ---------------------------------------------------- Ref:- http://javarevisited.blogspot.in/2015/01/difference-between-maven-ant-jenkins-and-hudson.html http://stackoverflow.com/questions/10834262/jenkins-and-maven-difference

Tuesday 14 July 2015

Top Java Blogs

http://www.yegor256.com/

http://www.javacodegeeks.com/

https://10kloc.wordpress.com/page/3/

http://www.adam-bien.com/roller/abien/

https://pragmaticintegrator.wordpress.com/

http://blog.arungupta.me/

https://blogs.oracle.com/reza/

https://blogs.oracle.com/theaquarium/

these are I personally feel good one above to all may be plenty of but . we can try these good for java developer.

Wednesday 1 July 2015

What is Agile Development approach.

What is Agile Development approach.

If I say in short. it's a Cheap,best and effective. mechanism,

Explanation.
70% we use scrum approach for Agile development which one of the popular way. rest are few.

Now question is what is
Scrum:-

Scrum is a way to restart the game after an interruption, where the forwards of each side come together in a tight formation and struggle to gain possession of the ball when it is tossed in among them

Scrum is just one of the many iterative and incremental agile software development method. You can find here a very detailed description of the process.

ref:-
http://stackoverflow.com/questions/11469358/what-is-the-difference-between-scrum-and-agile-development

in brief this is the way of developing the project.

few terminology we used in scrum.

Scrum master
Scrum
Sprint
Backlogs
these are the popular one.

functionality of scrum:-

1:-Scrum master:-
Represents management to the project
Typically filled by a Project Manager or Team Leader
Responsible for enacting scrum values and practices

Main job is to remove impediments

2-Scrum Team:-
Typically 5-10 people
Cross-functional (QA, Programmers, UI Designers, etc.)
Members should be full-time
Team is self-organizing

Membership can change only between sprints

3:-sprint:-
in product development, a sprint is a set period of time during which specific work has to be completed and made ready for review.
ref:-
or
A month-long iteration, during which is incremented a product functionality
NO outside influence can interference with the Scrum team during the Sprint

Each Sprint begins with the Daily Scrum Meeting

Daily scrum:-
Is a short (15 minutes long) meeting, which is held every day before the Team starts working
Participants: Scrum Master (which is the chairman), Scrum Team
“Chickens” and “Pigs”

Every Team member should answer on 3 questions

-----------------
Scrum Artifacts:-

Product Backlog
Sprint Backlog

Burn down Charts

Backlogs:-

A backlog is a list of features or technical tasks which the team maintains and which, at a given moment, are known to be necessary and sufficient to complete a project or a release: if an item on the backlog does not contribute to the project's goal, it should be removed;

product backlogs:

Requirements for a system, expressed as a prioritized list of Backlog Items

Is managed and owned by a Product Owner

Spreadsheet (typically)

Usually is created during the Sprint Planning Meeting

Can be changed and re-prioritized before each PM

note:-

Estimation of Product Backlog Items:

Establishes team’s velocity (how much Effort a Team can handle in one Sprint)

Determining units of complexity.

Size-category (“T-Shirt size”)

Story points

Work days/work hours

Methods of estimation:

Expert Review

Creating a Work Breakdown Structure (WBS)

sprint backlogs:-

The sprint backlog is a list of tasks identified by the Scrum team to be completed during the Scrum sprint. During the sprint planning meeting, the team selects some number of product backlog items, usually in the form of user stories, and identifies the tasks necessary to complete each user story.
or

A subset of Product Backlog Items, which define the work for a Sprint

Is created ONLY by Team members

Each Item has it’s own status

Should be updated every day

No more then 300 tasks in the list

If a task requires more than 16 hours, it should be broken down

Team can add or subtract items from the list. Product Owner is not allowed to do it

Burn down chart:-

Are used to represent “work done”.

Are wonderful Information Radiators

3 Types:

Sprint Burn down Chart (progress of the Sprint)

Release Burn down Chart (progress of release)

Product Burn down chart (progress of the Product)

---------------------------------------------------------------------------

pros/cons

Advantages

Completely developed and tested features in short iterations

Simplicity of the process

Clearly defined rules

Increasing productivity

Self-organizing

each team member carries a lot of responsibility

Improved communication

Combination with Extreme Programming

cons:-

“Undisciplined hacking” (no written documentation)

Violation of responsibility

Current mainly carried by the inventors

-------------------------------------------------

ref:-

https://en.wikipedia.org/wiki/Scrum_(software_development)

Thursday 11 June 2015

What is the Real Time Use Of Reflection in Java

Java: What scenarios call for the use of reflection?

Perfect Explanation from stackoverflow:-
http://stackoverflow.com/questions/9222621/java-what-scenarios-call-for-the-use-of-reflection?rq=1

http://stackoverflow.com/questions/25906480/how-does-reflection-in-java-affects-the-applications-performance-and-what-are-t
----------------------------------------------------------------------------------------------------------------

Real time Example Based on application..

here we are sending let consider 10 parameter to the action layer. now we need to get all 10 parmeter and set to any VO. the best solution is here is reflection see below.

Field[] fields=configureFieldsVO.getClass().getDeclaredFields();
String param = null;
String[] value = null;

if (fields != null &&CommonConstants.SHOW_DIV.equalsIgnoreCase(applyVTO.getBrandingInfoVO().getPrefellFlag())) {
notification.notify(new NotifyVO(NotificationConstants.INFO,"### Prefill Flag is enabled",this,Thread.currentThread().getStackTrace()[1].getMethodName() +
NotificationConstants.LINE +Thread.currentThread().getStackTrace()[1].getLineNumber()));

for (int i = 0; i < fields.length; i++) {
param = fields[i].getName();
if (param != null) {
try {
if (requestMap.get(param) != null && prefillData.contains(param)) {
value = (String[])requestMap.get(param);
setPrefillValue(applyVTO, param, value[0]);
}
}catch (Exception e) {
notification.notify(new NotifyVO(NotificationConstants.ERROR, NotificationConstants.EXCEPTION_ASSIGNING_VALUES,this,
Thread.currentThread().getStackTrace()[1].getMethodName()+NotificationConstants.LINE+Thread.currentThread().getStackTrace()[1].getLineNumber()));

}
}
}
notification.notify(new NotifyVO(NotificationConstants.INFO, NotificationConstants.CONSUMER_DATA_RECEIVED,this,
Thread.currentThread().getStackTrace()[1].getMethodName()+NotificationConstants.LINE+Thread.currentThread().getStackTrace()[1].getLineNumber()));

}
---------------------------------
private void setPrefillValue(ApplyVTO applyVTO, String param,
String reqVal) throws ApplicationException {
Field field = null;
try {
field =
applyVTO.getApplicantVO().getClass().getDeclaredField(param);
if (field != null) {
field.setAccessible(true);
if (reqVal != null) {
field.set(applyVTO.getApplicantVO(), reqVal.trim());
}
}
} catch (NoSuchFieldException e) {
notification.notify(new NotifyVO(NotificationConstants.DEBUG, NotificationConstants.FIELD_NOT_AVAILABLE,this,
Thread.currentThread().getStackTrace()[1].getMethodName()+NotificationConstants.LINE+Thread.currentThread().getStackTrace()[1].getLineNumber()));
} catch (IllegalAccessException e) {
notification.notify(new NotifyVO(NotificationConstants.DEBUG, NotificationConstants.FIELD_HAS_NO_PUBLIC_ACCESS,this,
Thread.currentThread().getStackTrace()[1].getMethodName()+NotificationConstants.LINE+Thread.currentThread().getStackTrace()[1].getLineNumber()));
}
}

Monday 8 June 2015

More new features coming to Java 9

Java is very wide. single word. Ocean..
Now it's depends how much you want for your comfortable zone.

It's very excited. we gonna soon see.

Java 1.9:

http://www.javaworld.com/article/2852123/java-platform/more-new-features-coming-to-java-9.html

Thursday 9 April 2015

What is LoadFactor and Importance of Load factor in java

As per java we should maintain it as .75 and initial capacity is 16.however we can increase it.
but this is the best because let we give it to Initial=100 and load factor=1
now total size to fill is 100*1=100;
two problem
1-it will take time to create 100 bucket size
2-there may be chance of waist of memory
now 16*.75=12
so advantage
1-it will take less time to crate 12
2-if at all chance of waist of memory then it would be less
again we need to increase the bucket size ,since it is create less bucket so we can bear it.not big size

more link:-
http://www.coderanch.com/t/261961/java-programmer-SCJP/certification/Default-load-factor

Saturday 4 April 2015

java 1.5 vs 1.6 vs 1.7 vs 1.8

try with resource
http://javapapers.com/core-java/try-with-resources/
http://www.theserverside.com/tutorial/Use-try-with-resources-Language-Enhancements-for-the-Java-7-OCPJP-Exam
http://javarevisited.blogspot.in/2014/04/10-jdk-7-features-to-revisit-before-you.html
http://javarevisited.blogspot.sg/2013/04/what-is-maximum-heap-size-for-32-bit-64-JVM-Java-memory.html
---------------------
2) Java 6 Features
A feature or an enhancement in Java is encapsulated in the form of a JSR. JSR, which stands for Java Specification Request is nothing but a formal proposal which details the need for a specific functionality to be available in the JavaPlatform that can be used by Applications. These JSR’s will be reviewed and released by a committee called JavaExpert Groups (JEG). This article covers the following list of features (or JSRs') that comes along with the Java 6 Platform.
Pluggable Annotation Processing API (JSR 269)
------------------------
Common Annotations (JSR 250)
Java API for XML Based Web Services - 2.0 (JSR 224)
JAXB 2.0 (JSR 222)
Web Services Metadata (JSR 181)
Streaming API for XML (JSR 173)
XML Digital Signature (JSR 105)
Java Class File Specification Update (JSR 202)
Java Compiler API (JSR 199)
JDBC 4.0 (JSR 221)
Scripting in the Java Platform (JSR 223)
-------------------------------------------------
J2SE 5 Features

The important features of J2SE 5 are generics and assertions. Others are auto-boxing, enum, var-args, static import, for-each loop (enhanced for loop etc.

For-each loop (Java 5)
Varargs (Java 5)
Static Import (Java 5)
Autoboxing and Unboxing (Java 5)
Enum (Java 5)
Covariant Return Type (Java 5)
Annotation (Java 5)
Generics (Java 5)
---------------------------------------------------------
JavaSE 7 Features

The important features of JavaSE 7 are try with resource, catching multiple exceptions etc.

String in switch statement (Java 7)
Binary Literals (Java 7)
The try-with-resources (Java 7)
Caching Multiple Exceptions by single catch (Java 7)
Underscores in Numeric Literals (Java 7)
---------------------------------------------------------------------
java 1.8:-
http://way2java.com/java-versions-2/jdk-1-8-features/

Sunday 29 March 2015

Why can't I define a static method in a Java interface?

There are two questions here:

Why can't interfaces contain static methods?
Why can't static methods be overridden?

link:-

Tuesday 10 March 2015

What is ServletRequestWrapper and How do we use it.

public class ServletRequestWrapper
extends java.lang.Object

implements ServletRequest
extends java.lang.Object
implements ServletRequest

Provides a convenient implementation of the ServletRequest interface that can be subclassed by developers wishing to adapt the request to a Servlet. This class implements the Wrapper or Decorator pattern. Methods default to calling through to the wrapped request object.
more:-

https://docs.oracle.com/javaee/6/api/javax/servlet/ServletRequestWrapper.html

This is the Best Link to knwo more about ServeltRequestWrapper

https://vangjee.wordpress.com/2009/02/25/how-to-modify-request-headers-in-a-j2ee-web-application/

Tuesday 3 March 2015

Jdbc 3.0 vs Jdbc 4.0

Jdbc 3.0:-
Jdbc RowSet We have done the great discussion on JdbcRowSet in the previous page.
Savepoint in transaction management Now you are able to create, rollback and release the savepoint by Connection.setSavepoint(), Connection.rollback(Savepoint svpt) and Connection.releaseSavepoint(Savepoint svpt) methods.
Statement and ResultSet Caching for Connection Pooling Now you are able to reuse the statement and result set because jdbc 3 provides you the facility of statement caching and result set caching.
Switching between Global and Local Transactions
Retrieval of auto generated keys Now you are able to get the auto generated keys by the method getGeneratedKeys().

Jdbc 4.0:-
The important features of JDBC API 4.0 are given below:
Automatic Loading of Driver class You don't need to write Class.forName() now because it is loaded bydefault since jdbc4.
Subclasses of SQLException Jdbc 4 provides new subclasses of SQLException class for better readability and handling.
New methods There are many new methods introduced in Connection, PreparedStatement, CallableStatement, ResultSet etc.
Improved DataSource Now data source implementation is improved.
Event Handling support in Statement for Connection Pooling Now Connection Pooling can
listen statement error and statement closing events.

Working with the JDBC RowSet API

ntroduction

RowSet interface is basically an extension of JDBC ResultSet and is a part of thejavax.sql package. Built on the standard contextual structure of the JavaBeans component model, the core design structure is inherently reflected in the subjectivity of RowSet interface. It makes sense that RowSet has a set of JavaBeans properties, which can be set and retrieved with the available setter and getter methods. In addition to that RowSet also implements the JavaBeans mechanism of event notification that allows other components registered to the instance to receive notification when a certain event is triggered. These additional capabilities make it more flexible and leverage productivity when used effectively. In this article we shall try to get a glimpse of what RowSet is all about and how to implement one in Java.

Types of RowSet

There are two types of RowSet objects – connected and disconnected. Connected RowSet are those which establish a connection with the database and retain it until the application terminates. Disconnected RowSet on the other hand establishes a connection, executes a query such as retrieving data from the database and closes the connection.

more you can get from here:-

http://www.developer.com/java/working-with-the-jdbc-rowset-api.html

http://javarevisited.blogspot.in/2014/04/Connected-vs-disconnected-rowsetprovider-rowsetfactory-and-rowset-JDBC-Java.html

http://www.javatpoint.com/jdbc-rowset

Why Need of serialization in Java

Serialization is usually used When the need arises to send your data over network or stored in files. By data I mean objects and not text.

Now the problem is your Network infrastructure and your Hard disk are hardware components that understand bits and bytes but not JAVA objects.

Serialization is the translation of your Java object's values/states to bytes to send it over network or save it.

This is analogous to how your voice is transmitted over PSTN telephone lines...

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A webservice requires serialization of objects to xml before they can be transmitted.

http://www.c-sharpcorner.com/UploadFile/jaishmathews/ApplySerializationinaRealLifeSituation03252006092701AM/ApplySerializationinaRealLifeSituation.aspx

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