Writing Comments in Java

Objective :

• How to write comments in Java?
• How to write single line comment in Java?
• How to write multi line comment in Java?
• How to write documentation comment in Java?
• What are the types of comments in Java?

Writing Comments in Java :

• Comments are the statements which are never executed (i.e. non-executable statements).
• Comments are often used to add notes between source code so that it becomes easy to understand & explain the function or operation of the corresponding part of source code.
• Java Compiler doesn’t read comments; comments are simply ignored during compilation.
• There are 3 types of comments available in Java as follows;

1. Single Line Comment
2. Multi Line Comment
3. Documentation Comment

Single Line Comment :

This comment is used whenever we need to write anything in single line.

Syntax : 

//< write comment here >

Example :

//This is Single Line Comment.

Multi Line Comment :

This type of comments are used whenever we want to write detailed notes (i.e. more than one line or in multiple lines)related to source code.

Syntax :

/*

< write comment here >

*/

Example :  

/*

This

Is

The

Multi

Line

Comment

*/

Documentation Comment :

• The documentation comment is used commonly to produce the javadoc for the respective program.
• The javadoc is generally HTML, if used in project it is a set of multiple HTML files describing each java program in the corresponding project.
• In the documentation comment we can add different notations such as author of the project or program, version, parameters required, information on results in return if any, etc.
• To add these notations, we have ‘@’ operator.  We just need to write the required notation along with the ‘@’ operator.
• Some javadoc tags are;
• @author – To describe the author of the project.
• @version – To describe the version of the project.
• @param – To explain the parameters required to perform respective operation.
• @return – To explain the return type of the project.

Syntax :

/**

*< write comment/description here >

*@author

*@version

*@param

*@return

*/

Example :  

/**

*This is Documentation Comment.

*@author Atul Palandurkar

*@version 1.0.0

*/

Shutting down 100 times faster

Hey frinds, do you want to Shut down your computer 100 times faster?

Procedure :

*Press ctrl+alt+del to open Task Manager

* Click the Shutdown Tab.

* Holding ctrl key, Press TURN OFF

Done!

Escape Sequences in Java

Objectives :

• What are the escape sequences in Java?
• What are the escape characters in Java?

Generally we enter all the characters directly. The escape sequences are used for those characters which cannot be entered directly.

Sequence	Purpose
\n	New Line (i.e. Line feed)
\b	Backspace
\t	Tab
\r	Carriage return
\f	Form Feed
\\	Backslash
\’	Single quote
\”	Double quote
\ddd	Octal Characters (i.e. ddd)
\uxxxx	Hexadecimal Unicode Characters (i.e. xxxx)
Escape Sequences in Java

Boost performance of computer/laptop

Objective :

* How to boost performance of computer/laptop?
* How to speed up computer/laptop?
* How to increase Virtual Memory of computer/laptop?
* How to increase performance of computer/laptop?

Procedure :

1. Right click "My Computer".
2. Go to "Properties" option from pop-up menu.
3. Go to "Advanced" tab.
4. Go to "Performnce" option.
5. Go to "Advancd".
6. Change "Virtual Memory" as follows :
    a. Kep Initial Size = Same
    b. Set Max Size = Double

How to get rid of Thumb.db file?

Objective :

* How to get rid of Thumb.db file?
* How to stop Thumb.db file from being created automatically?

If you don't want Thumbs.db File to be created automatically?

Steps :

Go to:
1. My Computer
2. Tools Menu
3. Folder Option
4. View Tab
5. Check the Option: 'Dont Cache thumbnails'

And its done!

If still your computer generates Thumb.db files then your computer must be affected from virus / worms, etc.

Separators in Java

Following are the some characters which are generally used as the separators in Java.

Separator	Name	Use
.	Period	It is used to separate the package name from sub-package name & class name. It is also used to separate variable or method from its object or instance.
,	Comma	It is used to separate the consecutive parameters in the method definition. It is also used to separate the consecutive variables of same type while declaration.
;	Semicolon	It is used to terminate the statement in Java.
()	Parenthesis	This holds the list of parameters in method definition. Also used in control statements & type casting.
{}	Braces	This is used to define the block/scope of code, class, methods.
[]	Brackets	It is used in array declaration.
Separators in Java

Operators in Java

In Java we are provided with number of different operators & these operators are further divided into arithmetic, bitwise, relational and logical groups.

Arithmetic Operators

The arithmetic operators are used to perform the arithmetic operations in algebra.

Operator	Operation
+	Addition
-	Subtraction
*	Multiplication
/	Division
%	Modulus
++	Increment
+=	Addition assignment
-=	Subtraction assignment
*=	Multiplication assignment
/=	Division assignment
%=	Modulus assignment
--	Decrement
Arithmetic Operators in Java

Bitwise Operators

The bitwise operators are used to perform the different operations depending upon the individual operators.

Operator	Operation
~	Bitwise Unary NOT
&	Bitwise AND
|	Bitwise OR
^	Bitwise Exclusive OR
>>	Shift Right with Sign Fill
>>>	Shift Right with Zero Fill
<<	Shift Left
&=	Bitwise AND assignment
|=	Bitwise OR assignment
^=	Bitwise Exclusive OR assignment
>>=	Shift Right assignment
>>>=	Shift Right Zero Fill assignment
<<=	Shift Left assignment
Bitwise Operators in Java

Relational Operators

The relational operators are used relate or to determine the relationship between the two operands.

Operator	Operation
==	Equal to
!=	Not equal to
>	Greater than
<	Less than
>=	Greater than equal to
<=	Less than equal to
Relational Operators in Java

 

Boolean Logical Operators

The boolean logical operators are used combine the two boolean operands resulting in new boolean value.

Operator	Operation
&	Logical AND
|	Logical OR
^	Logical Exclusive OR
&&	Short-circuit AND
||	Short-circuit OR
!	Logical Unary NOT
&=	AND assignment
|=	OR assignment
^=	Exclusive OR assignment
==	Equal to
!=	Not equal to
?:	Ternary If-Then-Else
Boolean Logical Operators in Java

The ? Operator

This is the special ternary operator in Java which is used to replace certain types of if-then-else statements.

Syntax :-

expression1 ? expression2 : expression3

 

If expression1 results boolean value true then, expression2 is executed otherwise expression3 is executed.