APEX :

APEX :
Apex is built on the Force.com platform and therefore it is plugged into other Force.com features.Apex allows developers to create highly complex, transactional and intelligent code.Apex is strongly tied with data structures and business logic needs.

Apex Benefits

Apex is governed and can only do what the system allows.Differences between apex and java

Classes and Triggers are two primary components constructed within salesforce when you write the apex code.When developers save apex code they always save it as a class or a trigger.

Apex is a proprietary language that sits within the Force.com platform and it can be invoked through triggers and classes.How to invoke apex

Syntax looks like this

Apex architecture looks like this

If the declarative features do not provide the  required functionality ,developers can use apex.

Use cases :

and a simple Hello world apex class and trigger
public class HelloWorldPositionClass {

public static void helloWorld(List<Position__c> positions){

for (Position__c p:positions){
if (p.Hello__c != 'World') {
p.Hello__c = 'World';
}
}
}
}

trigger HelloWorldPositionTrigger on Position__c (before insert, before update) {

    List<Position__c> positions = Trigger.new;

HelloWorldPositionClass.helloWorld(positions);

}

Summary of apex