• Coding Standards(CS) and Naming conventions(NC) are suggestions given by sun(Oracle).
• CS and NC help developers to develop projects with more readability and understandability.

Why Coding Standards?

• A program is written once , but read many times
  1. During debugging
  2. When adding to the program
  3. When updating the program
  4. When trying to understand the program

• Anything that makes a program readable and understandable saves lots of time , even in the shot run.

Naming Conventions: 

1.Naming a class:

• Class name should be "noun", because it represents things
• Class name should be in title case , means Every word first letter should be capital letter.
• This is also known as UpperCamelCase.
• Choose descriptive and simple names.
• Try to avoid acronyms and abbreviations.

2.Naming a Variable:

• Variable name also should be noun, because it represents values.
• Variable name should be start with small letter. 
• Use lowerCamelCase.
• Example: firstName, lastName, age.
• For final variable all its letters should be capital and words must be connected with "_".
• Example:  MAX_COUNT, MIN_COUNT.

3.Naming Method:

• Method name should be verb because it represents action.
• Use lowerCamelCase for naming methods
• Example: setFirstName(), getFirstName(), getLastName().

4.Naming a package:

• All letters should be small 
• like in java io, util, applet
• Example com.instanceofjava

• If you do not follow all above naming conventions compiler wont any Error or exception.
• But naming conventions are  useful in project and need to follow.
• But we need to follow some identifier rules as follows.

Identifiers:

• Identifier is the name of the basic programming elements.
• class names, methods names , object names and variables names are identifiers
• If we define a basic program without a name , compiler throws compile time error.
• Compilation Error : <identifier> expected.
• if we take a class without name then compile time error will come : Syntax error on token "class", Identifier expected after this token.

Rules in defining identifier:

• While defining identifier we must follow bellow rules, else it leads to compile time error.

1.Identifier should only contain :

1. Alphabets(a -z and A-Z)
2. Digits (0-9)
3. Special Characters ( _ and $)

2.Identifier should not start with a digit:

• A digit can be used from second character onwards.
• Example : 
• 1strank : throws error
• No1Rank : works fine

3.Identifier should not contain special characters except "-" and "$":

• Example : 
• first_name : works fine
• first#name : throws error

4.Identifier is case sensitive :

• identifier is case sensitive
• For example a and A are different a!=A.

5.keyword cannot be used as user defined identifier :

• we can not use keywords as our identifiers
• For example int class; // Syntax error on token "class", invalid VariableDeclarator.

Note:

• we can use predefined class names as identifiers
• example : int String;
• There is no limit in identifier length.

Java comments:

• A description about a basic programming element is called comment.
• Comments are meant for developer, to understand purpose.

Types of comments:

• Java supports 3 types of comments

1. Single line comments  - //
2. Multiline comments  - /* */
3. Document comment - /** */