Java Tutorial

Get MAC Address using Java

Free Source Code

Free Source Code

Objective :

* How to get the MAC Address of a computer?
* How to get the MAC Address of a computer using Java?
* How to get the MAC Address of a computer via programming?

[sourcecode language=”java”]
import java.net.*;

class GetMac
{
public static void main(String arg[])
{
try
{
InetAddress address = InetAddress.getLocalHost();
NetworkInterface nwi = NetworkInterface.getByInetAddress(address);
byte mac[] = nwi.getHardwareAddress();
System.out.println(mac);
}
catch(Exception e)
{
System.out.println(e);
}
}
}
[/sourcecode]

Note : This code will return only the first net address; if you need other detils too, get a list.

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Architecture of Java Program

Objective :

  • What is architecture of Java program?
Architecture of Java Program

Architecture of Java Program

While writing a java program, the above architecture need to be followed.

As the figure describes, documentation part or writing comments into program is completely optional. If you want to know, how to write comments & documentation in java? Click here

If the programmer wants to keep class in some package then only he/she will declare the package.

If we need to link any other class from some package then, we will write import statement otherwise if the classes are in same package there is no need of import statement.

Whereas class definition & program body is compulsory which will have your actual code.

Data Types in Java

In Java there are total 8 data types available which are further divided into 4 groups viz. integers, floating point numbers, character & boolean values.

Type

Size in Bytes (Bits)

Range

Default value

Contains

Integers
Byte 1 byte (8 bits) -128 to 127 0 Signed Integer
Short 2 bytes

(16 bits)

-32768 to 32767 0 Signed Integer
Int 4 bytes

(32 bits)

-2147483648 to 2147483647 0 Signed Integer
Long 8 bytes

(64 bits)

-9223372036854775808 to 9223372036854775807 0 Signed Integer
Floating point numbers
Float 4 bytes

(32 bits)

-3.4e38 to 3.4e38

(i.e. 3.4*1017)

0.0 IEEE754 Floating point number
Double 8 bytes

(64 bits)

-1.7e308 to 1.7e308

(i.e. 1.7*10151)

0.0 IEEE754 Floating point number
Characters
char 2 bytes

(16 bits)

\u0000 to \uFFFF \u0000 Unicode Characters
Boolean values
boolean 1 bit Not Applicable False true or false

Table : Data Types in Java

 

How to set Path for Java

Dear Friends,

If you want to set the path for Java, there are two main types for setting system path for Java which are as follows;

  1. Temporary Path
  2. Permanent Path

For the above two types, the video describes the complete step by step procedure for setting path for Java :

[youtube=http://www.youtube.com/watch?v=rM4Qq3Ua7Sk]

Or you can go through this tutorial :

1. To check path is set or not :
a. Go to Start Menu
b. Go to Run
c. Type “cmd” without quotes to open Command prompt.
d. Get to the root directory say c:/>
e. To check whether the path is already set or not, on command prompt type “javac” without quotes & press enter/return. If the following message appears on the console screen then the path is not set.

f. But if the other message having length nearly equal to half a page then path is set.

2. Temporary Path :

To set the temporary path follow the steps given below;
a. Open Command Prompt.
b. If path is not set &  want to set it temporarily, assume the Java 1.6.0 is installed on your system, type following command on console screen :
And finally the path is set temporarily.
Note : This will work only for the current window, won’t work if you open another window.

3. Permanent Path :

To set the path permanently follow the steps given below;
a. Right Click on “My Computer Icon”.
b. Go to “Properties”.
c. Go to “Advanced” tab.
d. Click on “Environment Variables”.
e. Go to “System Variables”.
f. Find “Path” variable, select it & click “Edit”.
g. Small window will appear. Go to end by simply pressing “End” button & type following path with semicolon ( ; ) as prefix but without quotes;
    “;C:\Program Files\Java\jdk1.6.0\bin
h. Press “OK”, again “OK”, again “OK”.
And finally the path is set permanently.
i. To check whether the path is set or not simply refer details given above in the section 1.

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 :

[sourcecode language=”java”]
//This is Single Line Comment.
[/sourcecode]

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 :  

[sourcecode language=”java”]
/*
This
Is
The
Multi
Line
Comment
*/
[/sourcecode]

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;
    1. @author – To describe the author of the project.
    2. @version – To describe the version of the project.
    3. @param – To explain the parameters required to perform respective operation.
    4. @return – To explain the return type of the project.

Syntax :

/**

*<write comment/description here>

*@author <write author name>

*@version <write version here>

*@param <write parameter here>

*@return <write return type here>

*/

Example :  

[sourcecode language=”java”]
/**
* This is Documentation Comment.
* @author Atul Palandurkar
* @version 1.0.0
*/
[/sourcecode]

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

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.

Keywords in Java

In Java there are total 49 keywords are available.

The keywords “const” & “goto” are reserved & not used.

The “true”, “false” & “null” are values.

One cannot use the keywords for any other purpose.

Following are the keywords in Java:

abstract assert boolean break byte
case catch char class const
continue default do double else
extends final finally float for
goto if implements import instanceof
int interface long native new
package private protected public return
short static strictfp super switch
synchronized this throw throws transient
try void volatile while ——

Keywords in Java

Features of Java

Objective :-

  • What are the features of Java?
  • What are the key features of Java?
  • Which features are supported by Java?
  • What Object Oriented Features (OOPs features) of Java?

Following are the key features of the Java Programming Language :-

  1. Platform Independent
  2. Simple
  3. Object Oriented
  4. Robust
  5. Distributed
  6. Portable
  7. Secure
  8. Multithreaded
  9. Compiled & Interpreted
  10. Automatic Garbage Collection
  11. Built in Networking
  12. Dynamic Operations
  13. High Performance
  14. Free From
  15. Free Editor
  16. Case Sensitive

Platform Independent :

The concept of Java is “Write Once, Run Anywhere”. Here the term platform refers to the operating system, to run any java program we need JVM (Java Virtual Machine) and is not dependent on any of the tools & components provided by the operating system, therefore Java is platform independent.

Simple :

It is simple to understand i.e. user can write & update the code easily since many syntaxes are similar to C & C++, hence they are familiar too. Java also eliminates the several poor programming features of C & C++ like goto statements, header files, structures, operator overloading, multiple inheritance and pointers.

Object Oriented :

Java is based on the concepts on Object Oriented Programming Language such as Inheritance, Encapsulation, Polymorphism, Dynamic Binding, etc.

Robust :

The Java is strongly typed & allows the Java Compiler checks the program whether there any error and the Java Interpreter checks any run time error and makes the system secure from crash. These features make the java language robust.

Distributed :

Java supports different network connectivity such as HTTP, & FTP. They are also built in Java.

Portable :

The java language portable provided that the system must have interpreter for the JVM. Java also have the standard data size irrespective of operating system or the processor.

Secure :

Java does not use memory pointers explicitly. Programs run inside the virtual machine sandbox. Bytecode verification process in Java to ensure that the code loaded over the network does not violate Java security constraints such as;

  • No memory pointers
  • Array index limits
  • Access restrictions, etc.

Multithreaded :

Java supports multithreading. Thread is nothing but the Lightweight process. When two or more than two threads runs concurrently, then they are said to be Multithreaded. Java also support synchronization of threads.

Compiled & Interpreted :

Java requires two steps to run a program;

  1. Compilation &
  2. Interpretation

The Java Compiler (javac) compiles the java code & produces the bytecode. The file generated after successful compilation containing the bytecode is known as Class file (“.class”) or Byte Code File.

The generated class file is then interpreted by the Java Interpreter (java) which gives the output.

Automatic Garbage Collection :

Java supports automatic memory management, it is done by JVM.

Built in Networking :

Java support networking as of it was designed keeping networking in mind & has many classes which help to create network & internet applications very easily.

Dynamic Operations :

Java supports various dynamic operations on demand such as;

  • Linking of files from all over the world
  • Loading of new classes & libraries
  • Compilation of classes & libraries, etc.

High Performance :

Java uses native code & “just-in-time compiler” which converts the bytecode to machine code & since java is interpreted it gives high performance.

Free Form :

It is a free form language i.e. we can write multiple statements in a single line.

Free Editor :

It is free editor language i.e. we can edit Java programs in Notepad, Text pad, Dos editor, WordPad, VI editor, etc.

Case Sensitive :

Java is a case sensitive language i.e. it differs in small letters & capital letters.

All the above are the main features of the Java programming language.