Java(Java Development Kit)

Java 8 has possibly the faster adoption rate of any new version date because of Lambda expression. if you will develop the java base application of course you needed a JDK to get started.The JDK includes the Java Runtime Environment ,the java compiler and the Java API. It's easy for both new and experienced 
programmers to get started.

You can easily download and install Java 8 on windows and linux platfrom.

Java Developers Tool Eclipse

Eclipse is Open-source integrated development environment (IDE) tool.It’s particularly popular among enterprise developers due to it’s large developer community and extensible plug-in system for customizing the environment.
Eclipse used to develop application in other programming language via plugins ,including ABAP ,C,C++,JavaScript,PHP etc.

List of Eclipse-Based Software :

The Eclipse Platform can be extended by adding different plugins for example

•  Adobe ColdFusion Bulder
•  Adobe Flash Builder
•  BIRT Project
•  EGradle
•  Code Composer Studio
•  google Plugin for Eclipse
•  IBM Rational Applicaition forWebSphere Software
•  MyEclipse
•  PHPEclipse
•  Rad Hat Jboss Develiper Studio
• SpringBoot(STS) 

  many more Plugin are available .

Eclipse are divide into three parts: 

Workbench : The Workbench acts as the starting point to the IDE.

Workspace : Workspaces group projects, files, and configuration settings under a single directory. 

Perspective : Perspectives define the tools, views, and settings available in the Workbench based on the context of the workspace. 

Classes and Objects

Java is an object oriented programming language.it resolved complex probleams into smaller sets by creating objects.
This objects provide two characteristics:

1. State
2. Behavior

 Bellow are few examples:

1.Door is object
  1.It can be in close or open state.
  2.You can turn close and open door (behavior).

3.Car is an object
   1. It has gear ,four wheels, 4 door etc status.
   2. It has breaking ,acceleration ,changing gears and open/close door etc. behavior.

Java Class:
Class is the core of java language.A class is a template or blueprints that is used to create objects. Class representation of object and the sets of operation that can be applied to such objects.class consists of Data members and methods.

let's take a few example:

Syntx: 
      public class {
        Data Members:
        Methods;
      }

Example:
       public class Student{
         String name
         int rollNo
       }

 Private,Protected and Public are called visibility levels 
 The members that are declared private can be accessed only from within the class.
 public members can be accessed from outside the class also.

Java Objects:


In above example Student student =new Student()://student is instance/object of the Student class.It will take memory in heap area and new operator dynamically allocates memory for this object.


when an object initialized ,it's called an instance. Each instance contains its own copy of these variable For Example: name and age are variable for object student is different.

This is a basic introduction on java Class and Objects.Check these chapters in sequence to learn more:
 Java Methods.
 Java Constructors
 Java Access Modifiers.
 Java this Keyword

 Java garbage collection.

ATG eCommerce

ATG is a leading provider of eCommerce software and related on demand commerce optimization applicaiton, and headquartered in Cambridge,MA  
It's the framework which comes up when ther is eCommerce implementation for high scale companies not used for small scal comanies as implementation time and resource cost will be high.Some of the Companies I know which uses ATG are Wallmart,AT&T,Best Buy,J.C Penney,Tesco , Vodafone, Lexixnexis, Verizonand T Mobile. IN 2015 ,Oracle released the Oracle Commerce Cloude a next generation ,cloud-based e-commerce platform.

Most of the online shopping application are migrating to Oracle ATG for the best perfomance of their website and for the customer satisfaction who visits to the website for online shopping.

For Developer respective,
Is's critical to grasp the ATG module like as ORM,Droplet for few,Shopping Cart, Personalization ,Catloge management.There are lots of modules like as BCC,ACC and CSS which will take good amount of time to good knowledge on those.I have explain some of critical points bellow.

ATG Nucleus
ATG Configuration Layering
ATG Config Path
ATG Component Scopes And Rules
ATG Custom Droplet
ATG Implicitly Modules
ATG Maintain Profile for Guest or Anonymous User
ATG Scenarios and Targeters Different
ATG Application Between Session
ATG Custom Price Engine
ATG Custom Servlet Pipeline
ATG CartModifierFromHandler And ShoppingCartfromHandler DIfference
ATG Repository API
ATG Repository ,Item descriptor properties
ATG Commerce Order, Shipping, Payment Status Code
ATG Repository Basic Description
ATG Repository web services
ATG  Installation And Configuration guide 10.1
ATG Configuration With Eclipse 
ATG Repository Caching
ATG Pricing Calculator 

References

Oracle and ATG

Java 8 Installation In Linux

Step 1 – Download Latest Java Archive

Download latest Java SE Development Kit 8 release from (http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html) download page or use following commands to download from shell.

[root@sn02 java]# cd /opt/

[root@sn02 java]# wget --no-cookies --no-check-certificate --header "Cookie: gpw_e24=http%3A%2F%2Fwww.oracle.com%2F; oraclelicense=accept-securebackup-cookie" "http://download.oracle.com/otn-pub/java/jdk/8u151-b12/e758a0de34e24606bca991d704f6dcbf/jdk-8u151-linux-x64.tar.gz"

[root@sn02 java]# tar xzf jdk-8u151-linux-x64.tar.gz

Step 2 – Install Java 8 with Alternatives

After extracting archive file use alternatives command to install it. alternatives command is available in chkconfig package.

[root@sn02 java]# cd jdk1.8.0_91

[root@sn02 jdk1.8.0_91]# alternatives --install /usr/bin/java java /opt/jdk1.8.0_91/bin/java 2

[root@sn02 jdk1.8.0_91]# alternatives --config java

There are 4 programs which provide 'java'.

  Selection    Command

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

 + 1           /usr/lib/jvm/jre-1.6.0-openjdk.x86_64/bin/java

    2           /opt/java/jdk1.8.0_45/bin/java

*  3           /usr/lib/jvm/jre-1.8.0-openjdk.x86_64/bin/java

    4           /opt/jdk1.8.0_91/bin/java

Enter to keep the current selection[+], or type selection number: 4

At this point JAVA 8 has been successfully installed on your system. We also recommend to setup javac and jar commands path using alternatives

[root@sn02 jdk1.8.0_91]# alternatives --install /usr/bin/jar jar /opt/jdk1.8.0_91/bin/jar 2

[root@sn02 jdk1.8.0_91]# alternatives --install /usr/bin/javac javac /opt/jdk1.8.0_91/bin/javac 2

[root@sn02 jdk1.8.0_91]# alternatives --set jar /opt/jdk1.8.0_91/bin/jar

[root@sn02 jdk1.8.0_91]# alternatives --set javac /opt/jdk1.8.0_91/bin/javac

Step 3 – Check Installed Java Version

Check the installed Java version on your system using following command.

[root@sn02 jvm]# java -version

java version "1.8.0_91"

Java(TM) SE Runtime Environment (build 1.8.0_91-b14)

Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)

Step 4 – Setup Java Environment Variables

Most of Java based application’s uses environment variables to work. Set the Java environment variables using following commands

Step 4: Setup JAVA_HOME, JRE_HOME and PATH environment variables

Use bellow the command for this.

export JAVA_HOME=/opt/jdk1.8.0_151

export JRE_HOME=/opt/jdk1.8.0_151/jre

export PATH=$PATH:/opt/jdk1.8.0_151/bin:/opt/jdk1.8.0_151/jre/bin

Also put all above environment variables in /etc/environment file for auto loading on system boot.