What is Apex?
This is a strongly typed object-oriented, on-demand programming language. Syntax looks mostly like Java and acts like stored procedures.
To know more about this language See below posts.
Apex Programming Introduction
Keywords used in Primitive-Collection Types
Class, Abstract, Implements, extends, interface keywords
With sharing & Without sharing keywords
public,private,protected & global keywords
Static, Final, this, super keywords.
Exceptional Handling -try, catch, finally, throw keywords
if, else, do, while, for, break, continue
Database Manipulation operations – insert, update, upsert, delete, undelete & merge
Simple Class to understand
Sending document as attachment
Inbound Email Service
Batch Apex in salesforce
Database.executeBatch-To Run job
Batch Apex Example
How to export data in .csv by using code?
job schedule in Salesforce by using Apex
Salesforce Governor Limits
Manage Salesforce Governor Limits
What is trigger?
More Example for practice:
Insert Records into Salesforce Custom Objects
Deleting records of an object using table
Checking Accounts Contacts
Detail Page Display using Action Support
Records cloning using clone() method
Wrapper class for displaying the selected records
Tabs – apex tab panels Example
How to insert multiple records at a time?
How to Display related contacts using inputfield?
SENDING eMAIL TO ALL CONTACTS OF An ACCOUNT
Creating picklist using
Wrapper class for displaying Int and String Data types
There are many other concepts in this Programming. Above are few of the basic concepts to understand.